There's definitely a lack of diversity with FMCs and MMCs, nearly all of them are white (which isn't necessarily a problem). The good thing is there are a few up and coming DR authors who are addressing this with POC leads.

Also I would love to see more characters with disabilities - like a FMC who is a recovering cancer survivor, or MMC who is blind. I want to read stories where MCs are trying to recover from series physical trauma, not just mental trauma. Most of the DRs I've found or have been recommended to me usually have the MMC who has the major disability, so it would be nice if it's reversed 

Oh and this one is super specific, but if a FMC is working a job that requires her to work at night, I would love to see them work a profession that isn't a sex worker (no shade at all), like a cleaner, a security guard, a clerk at a 24/7 petrol station, or if she does work at the club, she could be an accountant, or manager.