Hi folks, I found this thread interesting, since I've been developing a balance patch and collaborating on community members from each character. I'm always eager to read balance conversations.
You can see the changes made to him so far here (as well as all the other changes):
https://docs.google.com/document/d/1hWJkG4FEJt_YiHkwG9TlEAN94k2gYxt9dKO-r2sy5Iw/edit?usp=sharing
I'll go over everything in this with my own opinion as I did with OP:
The buffs to make jab more consistent actually seem fine - though you do toe a line in hindsight where you risk making Jr's jab
more obnoxious than Bayonetta's and that's definitely something I'd worry about when balancing it. Changing one of the worst jabs in the game to one that potentially consistently links into 20% damage from frame-4 is a huge difference, not to mention it will still KO at mid-100%. Again, it would be a good buff, but there are probably less polarizing ways to buff jab now I think about it (*cough* Jab-1 / Jab-2 is still pretty awful, even with a good rapid jab *cough*). I'm likely overestimating the weight of the jab buffs, though I do think jab is a big problem for Jr. so I really don't know if a more consistent jab would be that bad or not - I personally would like to see it, as stated before - especially when he has such bad close-range options right now. This is one that in theory sounds okay, but in practice could be totally make-or-break. Regardless, it would definitely be worth the trail run.
As for the D-Smash buff, it seems... Weird? We honestly already have two pretty good Smash attacks (F-Smash is strong and actually kind of safe on shield, while U-Smash is frame-7 vs grounded opponents, frame-10 otherwise.) and D-Smash isn't really that necessary for us to cover ledge options either. A highlight on why you chose this one would be appreciated, but it honestly feels out of place, so I can't really say much... It is one of our better KO moves, but keeping it as a read-heavier option might just be fine, so I don't feel it to be that mandatory.
--aaand on to grab buffs... Yeah, as stated, I'm not a fan of giving Jr. grab buffs. People complain about Jr's grab being bad, and while I'm convinced it's basically one of the worst in the game, it never feels like a crippling weakness when I play Jr., and I'd sooner give Jr. more interesting options with shields (Both OOS and against them.) than just improve his grab. As I noted before in this thread, grab buffs feel kind of arbitrary and I don't want Jr. to become "just another half-grappler" for the sake of it. -and while I know the buffs proposed aren't
that extreme, I'm still just really against giving Jr. "one of those buffs" unless you have a very solid reason to improve his grabs over other moves that could fulfill the same role.
Then there's a cannonball buff which?.. Makes it faster? I dunno, I guess? Seems, again, kind of arbitrary though. Making cannon faster won't really give it more or less use unless you do something crazy with it. Though if the change is just to fix the inconsistency of it not charging exactly the move actually starts (Which is what it looks like, you might have to clear this up.), then that's okay enough, but it doesn't feel like anyone will notice regardless, which is kind of a shame. I do like it, it just seems so minor. lol
As for the Mechakoopa buffs, it's an interesting one, and I actually feel like this one would be both noticeable and fair. The more I think about it the more that I feel that speeding up deployment of Mechakoopa would be one of the more balanced ways to make the move more consistently usable without actually making it a stronger tool. It would also give us faster access to things like Mechakoopa bouncing and shield pressure options, so while I'm not totally on board the "Mechakoopa needs to be better" train, I think this isn't so farfetched an idea that I could say no to it.
--and then we get onto the list of param changes, which I'm not going to really pay that much mind to in fear of popping a blood vessel in frustration while screaming "blanket buffs" at my screen. That said, there is one that I do really agree with - and that's the landing lag on N-Air. N-Air is a pretty good move, honestly, but the lack of opportunities we have to safely utilize it, especially when falling are holding it back a fair amount. I feel like shaving a frame or two of land-lag off N-Air specifically might actually be a very noticeable and positive buff. But if you couldn't tell I'm really not a fan of any of the others and that's the nicest way I can put it without 50 variations of "Why?" and a lot of being censored.
Overall, it's... -okay stuff. Nothing that I'm looking at and going "Wow, these are really original ideas for ways to buff Jr. that feel fair and balanced without being arbitrary." but it is in the right direction compared to most ideas on how to buff Jr. -and I actually feel that the proposed Jab, Mechakoopa and N-Air buffs would go a decent way by themselves to making Jr. better as a character.
Still, feel free to convince me otherwise on the ones I disliked, I'm actually pretty open to hearing why you chose these specifically as it looks like you have a pretty organized project going on, and I'm always happy to try and contribute something of value to discussions like this even if I'm not the greatest voice of reason on it.