If you go through using him, Del doesn't hold it against you when he finally moves to Kally's Bar.
It doesn't matter, the way it reads, I still feel dirty for doing it. And fucking him once doesn't really help him - it's Kally who saves him, after all, you're really only given a chance to preach to Carver, which for some reason works. I actually don't understand why the pre-requisite is there. I really don't think an alternate path would be unreasonable. All we need is an option to get to know him simply by talking to him like a normal human being so we can talk to Carver (considering he already tells you what the deal is when you ask "Freebie?", that should actually be enough for the rest to make sense), one or two small lines when talking to Carver that maybe indicate you've taken Del up on the offer before (it actually seems to be purposely vague, as if you're supposed to be able to talk to her even when you haven't taken up the offer), and probably restricting the "feminize" option behind having fucked him.
None of his dialogue seems to make any reference to having fucked him before when he arrives on Canadia station, nor does does Carver really make much of a mention to it when you tell her that slavery is wrong and she should release Del. The only reason for restricting the talk with Carver behind fucking him I could find is that once you've talked to Carver, you can't take back your suggestion, so if you wanted the other options, and talked to Carver just out of curiousity, you'd potentially lock yourself out of those options, but it also seems like Carver should be open to Steele changing their mind, you just...can't right now.
Considering feminized Delilah is the only version that seems to have follow-up content that I've found, maybe there's supposed to be more stuff later that I don't know about. However, as it's written right now, it just feels like an arbitrary requirement, while also making me feel uncomfortable.