8 is what I keep on my second island, and it works for me. That allows me to have 1 of each personality, and since the Island is very small, it easier to place the houses without feeling like you're running out of space.
I agree with the seemingly general trend of the thread that I'd like 16, or like mentioned by rocketspruggs a couple posts ago, 15 like in the GameCube game. The current 10 just feels a bit too constrained and I'd like to have more. Admittedly, like oath2order hinted at, the island itself isn't that large, so I could even go for 12. There are a few more villagers who fit my island's theme but who either just didn't make the cut or have been replaced over time, so any additional plots would've been appreciated.
if they somehow increased the map size, I think I'd be down for the old cube crossing cap of 15. as is though, I think 10 is fine, if somewhat unfortunately small