Sign me up for getting rid of gender locked personality types as well as adding sub types to personalities! I think the absolute best way to improve would be to expand the existing personalities and flesh them out / divide them up more. But I'm totally not against more personality types (I love some of those mentioned here like the Punk and the Nerd!)
I would also like to see like a more "wild" personality? I don't really know how to put it. It's just be interesting if some of the animals acted a bit more like animals? Just outdoorsy type stuff and if they were into hiking / swimming / camping etc. Close to a Jock but I feel like jocks only ever talk about running laps lmao. I donno I haven't thought about this much but it kind of just popped in my mind. :3
Ideally I would prefer that they do away with the gender lock on the personalities like mentioned in the original post, but for the Japanese linguistic reasons that WaileaNoRei pointed out, that's likely not going to happen.
I don't have any particular personalities in mind that they ought to implement, but I do wish that they would add two more personalities in the future if they're going to keep the 10 villager limit in place. It would be better to not have to double up on some personalities and get repeat dialogue.