I have already posted these suggestions on itch.io, but I am reposting them here for better visibility, with some edits and additions.
1) Marriage with multiple slaves. This also could be available after you meet certain requirements (completing certain quests, reaching after certain influence points, siding with certain factions or religions etc.) even if it isn't available from the start.
2) Being able to impregnate someone other than your wife. This feels unnecessarily limited at the moment. (If you're feeling daunted by the idea of making lots of children at different ages, then don't worry. Most people interested in pregnancy are only interested in the act of impregnation and sex while pregnant. People's interest in this mostly stops after birth. Therefore, you don't need to design every single child. Just making a generic baby/girl/boy; should be more than enough. At least much better than limiting pregnancy content this much. Most people won't be playing this for years, let alone decades, so there's no need to worry about the children growing up either.)
3) More virgins. Only two girls (no, anal virgin only Michelle doesn't count) feels very limited and unrealistic. This could be affected by their age (teenage girls could be more likely to be virgins, and this chance could get lower for older slaves), their background (if their story mentions any experience, then obviously they can't be virgins, but on the contrary if there isn't any mention of such experience than no reason to be not a virgin), girls with Pure/Innocent traits (only Caitlin fron now afaik), and corruption of both girl and city itself.
4) Just like how there is a slave market for below-average (random) slaves (Watery Eyes), there also should be an above-average (random) slave market where only slaves above a certain value are sold.
5) Dunno if this is already planned but ending(s) (yes, preferebly multiple endings). Possibly depending on choices you make, quests you complete, and factions you side with etc. Of course, there shouldn't be a reason to not continue the game in sandbox mode after completing the game or postponing getting the ending as much as you want.
6) Threesome scenes with your two main slaves. Making images for every slave combination will be too much work, so generic images are good enough.
7) If you are planning to add more non-random slaves (slaves with full renders and a personal quest) please consider adding girls with body frames/types similar to 197 and 199. Because all non-random slaves (and almost all random slaves as well) out there range from petite to normal. There isn't even a single one like them.
Hope you read this. Keep up the great work!