It happened a couple of times recently that I had reached the max games vs an opponent (phanton obviously) and I couldn't report my win... 

Would it be possible to add the number of games remaining vs the opponent when you analyse him?
I understand it's my responsibility to make sure we have games remaining but it would certainly be a way to prevent such situations! What do you think? MI?

Yes sure.

Ah, really great idea Spaaztic +1 xD

MI, what about automatic PM's, with warnings, for things like if you are selected for PO and when you have 2-3 games remaining with someone as well as Spaazi's idea.