OOOOHHHHHH!!!!!! That's a good one.
I have a problem with this idea.
Bruce has always been pretty forward about his distrust in Supes. So much so he tried to convince Dick(nightwing at the time) that Superman was not a human and could not be trusted because he did not have the same restraints that humans have. Bats has always been very wary of Supermans agenda when it comes to protecting earth.
With that being said,I find it strange that Bruce does not feel the same way about Diana. She is technically from earth but she is also a god of sorts that would fall under the same catagory as Supes. She is an immortal that will outlive Bats a hundred times over. I would never buy a relationship between the two(it just doesn't work for me).
I have always thought that Batman(or Bruce) needed a normal relationshhip with a normal girl. He is so immersed in his alter ego that I think he needs someone to kinda "ground" him,as opposed to another super chick to complicate his life. He has been fighting alongside the strongest beings in the universe now for 40 years and I think he may actually start to believe he is one of them(which I'm sorry to say he is not). He is just a man with a lot of cool toys,he is not a god level character.
A fling between Bats and WW might make for a neat little story and would probably sell abunch of books,but as for longevity it just wont work.
Plus we all know that Supes and WW are destined to be together,just read Kingdom Come.
That's the way it should be.
TheBeyonder.