MarioMeteor
Smash Hero
So in short, you don't want to address any of Roy's flaws and you want him to remain subpar.Another small suggestion for Ike that I kinda forgot about/have better information about now.
Ike's standing grab is kinda balls. For a character supposed to reply on it so much its tied for 6th worst in the game at 72 pixels. How about increasing its range to 78, bringing it in line with Marth/Lucina/Corrin? Maybe bump up Robin's from 74 to 78 as well, or maybe even put Robin's beyond the rest of the FE crew at 80. He is using magic after all to assist his grab. Roy should probably go up from 74 to 78, complements his playstyle in general.
Also guys just... keep in mind with all of this: you shouldn't be aiming to change a character's playing style no matter how well intended it is. That's how you annoy fans of those characters. Meaning Ganondorf should not be a combo machine. Should also avoid completely changing things from what the devs clearly seem to want for general archetypes. Meaning Roy should not be getting a bunch of auto-cancels: the faster more agile FE characters don't get them due to the wide range on aerials + speed combo they have. Roy is no exception to this. Ike, Corrin, and Robin are the slower ones, thus are the ones looked at more for that sort of thing. I don't think Roy should be getting an increased sword length either.
As a general example for Roy, who appears to be more aggressively designed (even if it doesn't work the greatest atm and should probably focus on using his fast speed options to set up traps), I'd look at improving his grabs. Not his throws necessarily (I believe the Marth/Lucina/Roy trio are supposed to have overall meh throws outside of okay Uthrows as stock caps which makes a fair amount of sense for their designs), but make all of his grabs have another active frame at the start. So instead of standing grab being active on 7-8 make it 6-8. On top of that, shave off the recovery of his grabs a tad. Not a lot, but say make his standing grab have a FAF of 28 instead of 30. Those kind of changes would compliment both playing him more aggressively (can punish shielding his moves a bit easier, doesn't have as large of window to punish him for attempting to grab) and trapping.
From there I would improve his pummel damage a tad (Kurogane doesn't have that info sadly so I can't get exact detail) to give the grab more purpose. He has small ranges for combos or at least traps, but outside of those ranges he can still at least chip in some good pummel damage and throw the opponent into a bad spot.
Beyond that: the mobility buffs are good and compliment both aggro and trapping. Fixing Dancing Blade and buffing Aerial Blazer is all good. Minor buffs to sweetspots to make the more safe is fine. I'm not entirely sold on the FAF/Auto-Cancel increases on his other moves or the Bthrow buff. Nor am I sold on the angle changes or BKB/KBG changes. I'd need somebody who uses Roy competitively to really say if those are good changes or not.
Instead what I'd look at is buffing Roy's Dash to Shield time (also known as Dash Length). He's in the FE group that has 17 frames as that time (Ike and Corrin are the only FE characters without that). I'd move both Roy and Robin out of that range. Roy still has a lot of speed and probably shouldn't have it improved too much, but buffing it to say 14 frames puts him in company with Ness and Pikachu. Robin I'd probably move to 13, where Toon Link, Link, Pit, and Dark Pit are.
Truthfully I'd also nerf Corrin's Dash to Shield time. No real reason why he should be tied for best in the game with Sheik at 8, doesn't really make sense for the character. Probably move it to the large chunk of characters at 11. Maybe 13, depends on how Dragon Lunge gets nerfed because that thing absolutely needs a tap from the nerf hammer.