This is not a creative answer but, now that I've considered this question, I'd like to see today's Batman team-up with today's version of everyone he teamed up with in Brave and the Bold and in the order in which he teamed with them in that book.
That would include Earth-Two Batman, which wouldn't have been possible between CoIE and Death Metal but which would definitely be possible now.
All that said, I always really loved the unlikely/non-JLA team-ups like Deadman and The Creeper. They did for me what I think B&B was meant to do in introducing me to new characters and making me a fan of them for life.
In fact, when I was studying playwriting I had an assignment to write a screenplay (a very different animal) and I wrote mine about The Creeper because I remained fascinated by him.