Falco isn't that good. Anyone who has tried maining him at anything above low level play can understand this pretty clearly. Many on this board have proposed buffs such as mobility boosts, faster lasers, and other things, but most of these buffs will never happen because
A) They contradict Falco's design
B) Falco is already good online
It's clear that Nintendo wants Falco to be a slower, more aerial-based antithesis to Fox's fast ground game based rushdown style, and I don't think people on smashboards will convince Nintendo to change that archetype. So I think the most realistic buffs for Falco will be related to giving him strengths that don't contradict this archetype, and don't make him too strong. Immediately, I think of a character with a strong baiting & punishing game with strong grab conversions and grappling potential, similar to Luigi.
All it would really take to make a gameplan like this functional would be to give Falco a functional and rewarding grab. This even makes sense in the context of the developers' dichotomy between Falco and Fox, considering Fox gets virtually nothing off of grabs. If they wanted to go the extra mile, he could lose some endlag on his aerials, receive slightly more hitstun on his lasers, and maybe have slightly better dash speed and acceleration (just not as fast as fox).