I do think there really isn't an argument for putting roy over game&watch. I don't think it's terrible putting pichu over game&watch, like I said, just kind of iffy. But even then they're relatively guaranteed, relative to other low tiers. His best strength is his ability to have relatively guaranteed combos on fast fallers. Really the only good things pichu has as a character are his speed and combo game.
Pichu against Peach, Puff, and ICs are basically not winnable if the players are even sort of on the same skill level. Pichu always has some of the worst matchups of any character in the entire game. MewTwo and Game&Watch both have significantly better results than Pichu. Like I've never heard of an IC main putting ICs above peach so. If you wanted to take another approach where you look at frame data and neutral and punish, ICs still lose even though they have wobbling. Where as peach loses to fox and marth not nearly as badly and has roughly even matchups against falco and falcon. ICs have hard loses to both fox and marth and at bare minimum does not beat falco and falcon. So far peach and puff are even (even though IC sheik isn't as good for ICs as Peach ICs is good for peach). So basically puff just has a better matchup spread. But puff does, against ICs and especially Peach. And sheik doesn't have a super good matchup in the top eight. All her other matchups are only theoretically losing (falco, marth) if she even loses. Puff has one definite losing matchup, fox. The justification of puff being over sheik is pretty straightforward. Let me give some reasons for why the changes I made are better. Literally any tier list is opinion but it should be backed up by facts. But the character's regular appearance in top 8 at majors by players like Wizzy, S2J and N0ne show he's still up there. I still think how easily Falcon gets combo'ed is a major weakness, and Sheik and spacies can mess him up. Marth doesn't have any projectiles, nor does Puff, but both of those characters can find ways to approach still. I think Falcon's speed and platforms still give him a decent approach. More often they simply avoid the projectiles. It isn't like spacies are regularly using shine to actually reflect projectiles. While I agree projectiles can be an issue for Falcon you have to keep in mind with the exception of FD he can use the platforms to avoid projectiles and approach. His recovery isn't any worse than Sheik's (I think Falcon's is actually better bc at least he typically gets more opportunities to recover since Sheik is lighter). My 2 cents on the Falcon discussion is that while I agree his weight/fall speed and poor recovery make him easy to combo and susceptible to gimps he is still the fastest character and has a good combo game himself. I'd personally make a few adjustments like Puff > Sheik and if you put ICies in top tier then Falcon should be there too.
Lastly I think it would just be more accurate and I agree current tier lists are outdated. We could also be giving characters more respect i.e. I'm personally not a huge fan of tier lists in general but knocking Fox back down off of his own tier might reduce that "Fox is OP in Melee" stigma. I would really like to see a 25-man panel vote on a tier list so there could be an updated one. I still think the 2nd-5th order is debatable but I believe people would have Puff higher than 5th in the current meta. I'm more bothered by Fox having his own tier (at least on smashboards) and the Falco, Marth, Sheik, Puff order. Ganon gets wrecked so hard by certain characters so I don't think he's underrated but that's just me. I think yoshi is underrated but aMSa is also currently crushing it with yoshi so that makes the character seem even better. I agree with you about too many brackets. ^ Maybe something like that feels more current.