Personally, I would be a lot more cautious than some, not necessarily going like "RIGHT, WE'RE MAKING ONE HUNDRED TRIPLE A GAMES TO BE RELEASED BY NEXT WEEK"
For instance - I'd probably leave most larger series like Mario, Pokemon, Smash, etc to their own devices - though I'd personally be giving suggestions as to how they could be improved, etc. Maybe suggest popular inclusions and the like according to online and such.
My main thing would actually be "smaller" projects, overall.
Point One: The IP Resurrection Campaign
The idea behind this is that smaller, but still high-quality, titles would be made for IPs that aren't really active anymore. This could then be used as a sort of litmus test to see if the IPs are considered "popular" enough to warrant coming back in full force. Notably, we wouldn't pull a SEGA here - my idea is primarily based on general reception, with sales just being a backup for that sort of thing. Whilst there's absolutely tons of series you could actually do this for, the following are just a few of my basic ideas. Some series I didn't mention, but would love to see return in similar fashion, are Custom Robo, 1080, Wave Race, Doshin the Giant, Art Academy, Wario Land, Mach Rider, Excite, Diddy Kong Racing, Chibi-Robo, and many others.
Joy Mech Fight - Second Bout!
Essentially, a sequel to the original Joy Mech Fight, but with SNES-styled graphics and soundtrack - supposed to act as though this were a genuine sequel back in the day. It would bring back all of the fighters there, as well as a couple of new fighters and stages alike, as well as an all-new story. Being a smaller title, I can imagine it featuring in a Nintendo Direct as a downloadable title.
Punch-Out - REMATCH!!
This game is essentially an improved "remake" of the Wii title, though with basically every... feasible character from the Punch-Out series, in that sort of Wii-esque style. I also imagine that the "secret enemies" could, as well as Donkey Kong and Doc Louis, include the protagonist of Super Punch-Out (which we could even give a new name?) and maybe even an enemy from Teleroboxer, for the Virtual Boy.
Pilotwings/Switch Sports Resort
A... weirdly logical choice to me. Think of this as a sort of return to Wuhu Island, but with various intriguing changes. For starters, new sports such as those seen in Wii Sports could be added - as well as more air sports and the like as seen in Pilotwings. Also, I'd like to have Wuhu Island literally be an open world - so, you can just select the menu to be able to go to any sport instantly, but it's also possible to move across the world yourself in various vehicles such as bicycles, boats or even planes, and be able to go to the sports around the world.
Ultimate Game & Watch Collection
Think of this as, essentially, the ultimate collection of Game & Watch titles - similar to those seen back on the Gameboy, but for a new system. The idea is that a vast number of Game & Watch titles could be here (perhaps with Mr. Game and Watch as a sort of mascot?) as well as new games in the same sort of style! Notably, this is a smaller downloadable title.
Ice Climber - Reaching the Summit Together!
More of a game you play with two characters, the idea behind this is that it's similar in basic premise to the original Ice Climber - reach the summit, of course - but you can do it in various different ways with lots of branching paths and the like. It shines most of all in co-op mode - with you being able to either help, or hinder, your partner. Whilst this would likely be a much smaller downloadable title than most, I can see it being a pretty cutesy one in terms of style - think a mix between Popo and Nana in Smash, and the artstyle of Link's Awakening.
StarTropics 3 - Zoda's Disciple
Likely being released alongside the first two StarTropics titles, StarTropics 3 follows an alien of the same species as Zoda, who hails from the distant future and was inspired by the tales of Zoda's determination, seeking to kill Mike Jones by travelling into the past. I can imagine that this would be a weird series to bring back - and remakes of the first two with it in a Link's Awakening-esque style could be beneficial for this - but this could set up something like a Mother/StarTropics crossover game, which I'd absolutely be all for.
Point Two: ROMs and Emulation
I want to solve the ROM problem by doing something unprecedented. Whilst a Virtual Console could be cool, I don't honestly think it should be alone. Here's my proposal - Nintendo starts a section of their site which is dedicated to the purchase of ROMs. The idea is, it takes a form similar to something like an Amazon page, with a vast amount of ROMs listed (and I'm talking, like, ideally we want most of the libraries of the systems present.) You'd be able to sort them by release, alphabetically, etc, with each console in its own sort of subpage.
Then, if you choose to download a ROM (let's say Super Mario Bros,) you'd pay through the site with something like PayPal, and then be sent a .zip file by Nintendo with the ROM itself, high-quality scans of the instruction manual and other cool things like scans of the box art, etc. The idea is that external emulators can be used to run the ROM (which would have copy protection and such so you can't just distribute it freely) but Nintendo can still make profit off of it, which I think would honestly be the best of both worlds in terms of allowing game preservation and the like, plus it's a solution Nintendo's higher-ups might well actually agree to.
Point Three: "Deluxe" NES Titles
Loosely based on the 3D Classics line as well as NES Remix, this idea would essentially have NES games (and maybe SNES games too?) being "remade" in a sense, even if just to generally modernise their appearance. For instance - certain titles might have a more hand-drawn aesthetic (Zelda 1 and The Mysterious Murasame Castle spring to mind as good instances of this) but I'd also say that certain titles such as the Famicom Detective Club duology should be translated and released overseas as well.
Notably, this wouldn't be during the Switch's lifetime - as I can imagine that Nintendo want to milk the hell out of the Online system they have now - so it would likely be during the next console's lifetime, as small, inexpensive downloadable titles with lots of love and care - which could work alongside the Virtual Console releases, if you wanted, by giving the "Deluxe" editions some quality-of-life improvements and added bonuses over VC, which is just that. It could theoretically be extended to the SNES... but I personally wouldn't, at least until the NES is filled out a bit.
Point Four: Club Nintendo Returns!
I'd also like to bring back Club Nintendo - but have the Japanese style of it more common worldwide. Instead of more "general" rewards as seen in the US and UK, I imagine the rewards would be far, far more... Nintendo-esque. I'm talking like, adding stuff like a perfect replica of the Ultra Hand or the Napoleon hanafuda cards in there, as well as some of those really cool Japan-exclusive style rewards. The idea is, Club Nintendo is a club for fans - and I'd really want to lean into that with something like this.
Point Five: All New Developments?...
With smaller games being used as a basic litmus paper to bring back dead franchises, it's only fair that we bring one back in full force - after all, the DLC of Mario Kart 8 was a good instance to show that people were excited...
F-Zero ZX(?)
Set after AX and GX, but before Maximum Velocity, this would essentially bring back the F-Zero formula you know and love to the new generation. All 40 of AX/GX's characters return - as well as all of the Maximum Velocity characters coming in as secret bonuses (despite their dubious canonicity, I know) as well as some all-new racers to join as well, some of whom might (similar to James McCloud) be based on various Nintendo characters, such as Samus and perhaps some more unusual reference characters like Pit.
Notably, this title would bring in a ton of things from across the series as a whole, acting as a celebration of F-Zero in a way. As well as HD remakes of all of the F-Zero AX/GX tracks and most of the X tracks, I also imagine that certain SNES tracks would be brought back as bonuses too. Not only this - but the DD expansion tracks would come back too (including Rainbow Road!) as well as the ability to make your own tracks to play on, or even make your own racer/car as in AX/GX. Of course, there'd be plentiful new content too - so don't panic.
The main draws, as usual, are speed - with this game being just as fast as its predecessors, as well as having great multiplayer appeal - perhaps even being able to run 30 person online multiplayer if Nintendo ever fixes its online.
N64 Mini
Nope, I'm serious. The Mini line of consoles were actually loved by a wide amount of the people that managed to eventually get their hands on them, so I can imagine that this product could genuinely be pretty popular all told. Whilst some particularly popular games such as GoldenEye 007 might not be possible to get onto it, the cartridge-based format, as well as Rare's good relations to Nintendo, means I think we could probably get a wide variety of games - let's say around 24.
Kirby Air Ride HD Deluxe
Think of this as the "definitive edition" of Kirby Air Ride - a game criminally forgotten since its heyday on the GameCube. I'm not sure exactly what to add to this except similar to F-Zero ZX, with generally just more content added overall.
Gameboy Advance "Mini"
Similarly to the Mini titles, this is essentially another collection of GBA ROMs in a GBA-styled console - except this one differs in that it's meticulously designed to both replicate the best aspects of the GBA, as well as improving it with modern technology where it fails such as with its buttons and its screen. I honestly think that as many as 49 games could be a solid pick here, and the idea of the GBA getting the same treatment as the Game and Watch with its own, wonderful little replica, would be pretty cool to me at least.
Final Thoughts
A part of me kinda looks at all of this and... well, I feel a little melancholic. Nintendo is a company well known for making fans of its work - but the thing is, I'd love Nintendo to give a little more love to its fans, in a way. Whilst I wouldn't want to take away from bigger titles as they're being released, it's more that I'd love to see Nintendo really recognise the people that have grown to love it, as opposed to just seeing everyone as a customer in a sense. That's what I'd do, at least.