Sony and Warner Bros. can co-produce and co-finance this movie. This would not, obviously, be an MCU based film. It doesn't have to be "Snyder-Verse", either.
Andrew Garfield can play Peter Parker/Spider-Man
Henry Cavill can play Clark Kent/Superman
This can be a "megaverse" crossover film. Or... it could operate with the quiet conceit that both of these guys are on the "same" world, without controversy.
The criminals would have to be incredibly powerful. At least, from Superman's vantage point. Mongul, and, uhm... not sure what ultra-powerful villains that Columbia has spider-exclusive access to.
Sony wants more hits. WB wants more hits. They need to make this happen, once and for all.