HRH I see what you're saying but I think you're got yourself stuck into defending a position that doesn't really exist.
I'm reading your hypothetical situation as saying this: what if two people have slightly drunken but definitely consensual sex and then the next day the woman decides she didn't give consent even though she very clearly did at the time.
Have I got that right?
See, I think that kind of situation, where there is a 'retraction' of consent is rare.
In your hypothetical situation, where two people have mutually consensual but slightly drunken sex it would be unusual for her to change her mind the following day. Why would she? If she freely gave her consent at the time she'd presumably be as happy as he is in the morning. I think this goes on a lot and most people do not regret it.
If she changes her mind because her perception in the morning is so significantly different from the night before, then obviously she was somewhat more than slightly drunk. Therefore, she was vulnerable and incapable of giving genuine consent. You can only conclude that her partner has taken advantage (i.e. raped her).
If she changes her mind because of fear of consequences (i.e. makes a false allegation), well it happens but we've already established that it is incredibly rare.
I agree with you that two people can have slightly drunken sex without there being rape involved. I think in cases where a woman 'changes her mind' subsequently though, you will nearly always find that she probably wasn't just slightly drunk and that she was coerced or forced (i.e. raped).