Less jack of all trades characters. I saw a lot of those in some games and it discourages people from playing characters that are more specialized and people just debate between which jack of all trades is the best. Keep in mind, I think jack of all trades characters should 100% be present and have a place in games, but they shouldn't out do someone focused on mostly zoning or someone focused on rush down. The goal is play style variety and it would be nice to see designs focused on giving characters very SPECIFIC, INTENDED weaknesses and strengths to keep them in check. For example: Zoner might give rushdown a hard time, but zoners struggle versus counter zoners and counter zoners tend to struggle against rushdown.
I want character customization to be big. Injustie 2, Soul Calibur 6 and others have this and I love it because there's nothing like making your main your own, distinct character that nobody has exactly like yours. Creative freedom is always great to me.
Incentives to discourage rage quits whether that's time in a pool with rage quitters, reduction of in game currency or whatever will help give an incentive to reduce rage quitting while being reasonable.
We've seen a lot of racial diversity in games lately and I hope that trend continues as fighting games to me are about the variety and uniqueness of characters both gameplay wise and lore/design wise.
Frame data in game. Some game companies are very good at including this and it helps me learn so much quicker and especially with my being on a limited time frame I can look at my core, best buttons and form a gameplan around that as opposed to having to guess which takes much more time.
Although generally I haven't had too many problems with netcode in games, any improvements are ALWAYS welcomed.