But logically why? The classes are separated by race essentially. You'd have to wait for new class releases within the same race. Arbitrarily lumping races together because "cash shop is lonely" seems like a lot of effort for no real reason.
Who would be included where and why. Chances are the classes you personally want to share CS wouldn't even be combined.
It'd make more sense, and be more realistic, to ask for more frequent cash shop transfer events or opening up the race restrictions entirely.