Something I really want to see is a short-ish, but highly replayable Adventure mode with unique content across each stage.
I don't want something like Melee's Adventure mode. I thought it was kind of a waste of potential. With only a few sidescrolling stages packed among a ton of regular battles, it really felt like an extended, more scripted Classic Mode.
I don't want something like Brawl's either. I loved the thing, but at the end of the day, I played it once and never again. I want something shorter. Something more replayable. Something you can always go back to, that would still surprise you even after you played it dozens of times.
Picture this. The mode starts out very similarly to Melee's adventure mode, a short, sidescrolling stage based on the Mushroom Kingdom. You go through a few platforming challenges, defeat Mario enemies, maybe explore a bit to find random trophies, and reach the goal to end up in a "boss fight" against a Mario character.
Okay. Stage Clear. You're now taken to a sort-of map screen, and this is not actually a new concept.
You get branching paths. All paths lead to a completely new side-scrolling level, with challenges and enemies based on a specific franchise, and a "boss battle" at the end against one of the playable characters from that series.
The part where the fun comes from could come from having several pre-defined stages, but not necesarily having to play them all to reach the end. You get to choose. Like, for example maybe there's 10 stages in total, but you reach the end after you go through 5 of them.
And when I say branching paths, I don't necesarily mean you'd always have a choice. There could be different exits in each stage that open up extra choices in the map screen, or maybe by finishing up a stage with extra requirements could lead you in a totally different direction, or maybe even lead to skipping stages entirely. Think of it like a mini-Starfox, but with sidescrolling Smash levels. You could also hunt for secrets along each stage, and find **** like hidden bonus trophies, or even find optional fights or special events that could boost your score, or let you unlock special trophies. Like, find a secret barrel in the Donkey Kong stage, and you end up in a Break the Targets room. Clear it in 15 seconds, you get a unique Donkey Kong trophy. Just an example.
There's a lot of **** that could be done with this idea, and it'd be a hell of a lot simpler to develop than a full-blown story mode like Brawl had. The idea is that it'd be something you clear in 20-30 minutes, but would totally leave you wanting to play again to find other paths and secrets and ****, or to try out other characters. Also, two-player coop is a must!
That's all. Detailed and a bit too specific, but I'd love to see something along those lines.