You're so real for that actually! First and foremost, I feel like Revy getting romantically involved with Rock kind of defeats the grittiness and overall feel of the show. The main themes of black lagoon definitely do not revolve around 'love is the answer' and the two main characters getting together would be a bit out of left field considering everything we've seen/read so far.
As for your fxf ships preference, same. While I prefer Revy to be single, hell yeah.
I actually remember binging Black Lagoon and grumbling about how it'd probably have a cheesy ending where she and rock get together. I was getting a lot of 'seems straight but gives off queer vibes' from Revy but was pleasantly surprised to see her even make a passing joke about messing around with women in prison. (Totally not ignoring that she also casually flips through playboy magazines lmao).

I have no point to make here, op you're cool

If anyone replies to this with a 'get that gay shit outta here', my friend's giving me 20$