I'd love to see:
in the opposite universes
Batman, I would hope to actually set up shop as a city level vigilantie. Not as 'Bat-God' in the Marvel Universe. Have him trying to learn about the players, who is good/bad. His tech whilst good, is not as technologically advanced as Stark Industries etc. Dealing with guys like Bullseye, Batroc the Hand, Maggia, Mysterio etc.
Would be good to see him unpick the Hand. Have run ins with Shang Chi, Iron Man, Black Cat etc.
Doctor Strange is a natural fit in Vertigo. Have him stunned as the majority of his powers have disapeared (due to contracts with the Vishanti or calling on beings like Cyttorak). He has his own personal spells and must figure out the strange new rules on dimensonal travel. As well as navigating the differences between the realms of Order and Chaos. He would be fantastic on trying to draw on power from being slike Desire, Dream or Delirium.
Also - who wins Batman vs Dr Strange. 1 month worth of prep?
but I think I'd like to see Deathstroke and Dr. Doom switch places....I think Doom in DC would be very interesting...he'd be starting without all of his resources, but I'm sure he'd build an impressive power base quickly.
Likewise, I think Deathstroke would be interesting in the MU.
Taskmaster through the late 90's had a very strong track record, and back then, he may well have been REALLY interesting in the DCU as well...training villains etc....if I switched him out, I think I'd swap him with classic Blue Devil as he was during the end of his solo series, because I'd like to see him interact with some classic Spidey villains.