Dunno how financially feasible one-time purchases would be, but they'd be my preferred model. Some things I'd pay for:
- several tiers of verification, each with higher stat cap and higher price (something like 5$-10$-20$-50$), ofc if you already have a tier and want to upgrade you just pay the difference
- reskins for equipment, but instead of actually changing the item itself it's bound to the character bloodline, you just right click an item in equipment screen and select from a list of all skins you bought for that item and the item looks like that as long as you wear it
- unlocking specialty skills, ie everyone can learn all the basics, but to learn high end stuff like Jewellery or Silkmaking you have to unlock them by buying them for like 2-3$, as a one off purchase the unlock should persist across the character bloodline
- cosmetics for beautfying your settlement
Also, I think all of these should be per character slot.