Jeez AX is correct - I would pay for Sisters vs Hrud just for obscurity. Probably the same gene that made my Dad by an old oop book on WWI panzers for £80.

I would like to see Squats versus Ratlings. Because even if you buy the Homeworlds getting eaten* Squats were widely enough travelled to feature elsewhere. And scrapping with ratlings would be funny. Or failing that, something with Imperial citizens in it, getting eaten either by plague zombies, or possibly a single stealer.

* There is an article that debunks this theory, on the basis of the fact whichever GW person said about the homeworlds, later conceded that it was an entirely throwaway line and wasd not planned canon for squats. Vulcans in Star trek reboot - dead planet, lots in the galaxy. Works for Squats.