Story wise I would love to see a college setting allowing for mature/dark themes which we all seem to be a sucker for these days. In combination with that I would like to see the choice of choosing gender which creates two varied playthroughs in terms of available social links and perhaps other gameplay mechanics.
Aesthetically and for my personal enjoyment, I'd like to see the Velvet Room take place in a jet. So far we've had a regular wide room in P1 and P2, an elevator in P3, and a limo in P4.
Gameplay mechanics that I want are background leveling, having persona recipes available to you because some of those persona fusing requests got annoying cause w/o a guide it was hard to determine what personas you needed to combine and the option to cherry pick the move set of the persona fusion result at the cost of money. I literally spent one hour reshuffling to get the skills i wanted for Thanatos. I think paying for your ideal moveset seems fair and do something like with Fox where the service starts off expensive but have the person doing it have a social link and thereby decrease the cost at higher Social Link Lvls.
What do you guys think?