Now that a bunch of old Pokemon have larger menu sprites from Let's Go and SwSh, I think we should use them. They look really nice, and layouts will probably need to be adjusted anyway because of all the new mons that only have large menu sprites.
Like I said, even if the old menu sprites don't get updated, the layout would still need to be adjusted to accommodate the new mons that only have large menu sprites.I feel iffy about this, because Showdown! has decent support for smaller screens right now, but larger menu sprites has a shot as invalidating that. Either all of the sprites end up crammed together, or we make the screens that use them take up more space. Neither of those would be great outcomes.
Not to mention it would look weird because there's dexited mons who would most likely get these kinds of menu sprites who won't have them like Landorus-T and Heatran who would have their small menu sprites appear alongside mons that have larger ones like Clefable and Toxapex.
Downscaling the bigger sprites in a way that looks decent shouldn't be too hard to do. There's about 50 menu sprites that would need to be scaled down, which certainly seems feasible.Like I said, even if the old menu sprites don't get updated, the layout would still need to be adjusted to accommodate the new mons that only have large menu sprites.
National Dex OU is a thing and it has a decent playerbase as of right now, so this would be a concern for those players.How cut mons look shouldn't be a concern. After all, they were cut, and so don't ever appear in the main metas. Though I suppose visual consistency while playing in past gens could be a valid issue. Perhaps a mon's menu sprite could dynamically change depending on the generation, just like how the battle sprites and battle backgrounds are different for each generation.