I think it's also worth noting that our favorite EP, Alex Kurtzman, was (supposed to be) the architect of the whole Dark Universe/Universal Monsters revival a few years back. Universe building to bring about a massive crossover project is his thing.
With Chabon out (as showrunner), STPicard is more free to pursue fun little projects like this and can be on the forefront of a crossover project if need be. Discovery probably ought to solidify itself a little in their century, but it will be fun seeing them reunited (if only briefly) with their 23rd century friends.
The animated ones might be left out, or be part only in easter eggs or cameos. Or have their own crossover special (they could even use the holodeck for crossover cast from SNW and Discovery).