There'd still be complaints. People love to complain.
Plus, Roy has a very big fanbase here, more for his Melee appearance than his FE appearance. Chrom would be hated if he outright replaced him.
Plus, in terms of series representation, if you took out Roy it would look like this:
NES/SNES Era
![Marth :ultmarth: :ultmarth:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Shadow Dragon, Mystery of the Emblem
GCN/Wii Era
![Ike :ultike: :ultike:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Path of Radiance, Radiant Dawn
GBA Era
3DS Era
![Corrin :ultcorrin: :ultcorrin:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Fates
![Robin :ultrobin: :ultrobin:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Awakening
![Lucina :ultlucina: :ultlucina:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Awakening
![Chrom :ultchrom: :ultchrom:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Awakening
If you're simply arguing from a fighters' perspective, where unique movesets are all that matter, sure, your idea works. From a series representation perspective-- which is half of the purpose for Smash's roster-- it's definitely worse.