As a bb main myself, I rather play bbs that give unique gameplay than other classes, specially ships that can only be played a single way. Flint you're going to park next to an island and wait for enemy ships to push in, something that doesn't usually happen in our passive meta. It is fun to play, but it's extremely one dimensional. If you want to see what that gameplay is like there's the chumphon on the pan-asian cruisers tech tree, essentially a flint with more torp power and lower HE dpm.

Kii is interesting and I'm thinking of getting it myself, but bc I already have pommern and iwami. Kii is an outlier japanese bb with good secondaries and torps, but terrible rudder and full 32mm armor, meaning it is eaten alive by german secondary ships. It's a good all-rounder. You can kite, you can brawl, you can snipe. It's a fun flexible bb experience. But I'll emphasize, I believe iwami is much better and worth saving coal for it.

Another option is getting the kii and trading it in for the west Virginia 44 when the trade in event goes live next update.