I don't really get it if succubi already treat humans as one-use food, and if the growth problems are just because they don't instinctively eat... surely they could just teach em. The Bad Ends already show that Ichigo will go full Succubus if something naughty happens, and I don't think demons would give any second thoughts about the human-side ego disappearing.
There's the implication that they're more likely to have a half-child with a human but... is that a big deal? Succubi are already stated to be the usual choice for demon males for childmaking so unless half-Succubus mothers always give birth to 50/50 ratios or their pairing with fellow demons always results in half-humans, what's the big deal?
What's with the assumption that they must eat humans anyhow, surely they can get vitality from demons too.