*claps in applaud*
I hadn't even fathomed shipping these two before reading this. You're evidence on their possible romance has a good foundation, but I don't think you took the whole 'sexual aspect' to mind. I feel like these two would have issues with dominance.
Wheras (my OTP) Rei seems to show some submission to Nagisa.
But that's just my speculation~
All in all, you did a pretty good job with convinving me. I think I'll mention this ship of yours to some of my Free! fanatics （＾ω＾）