DDR has been a thorn particularly because they used a custom chip for decoding encrypted MP3 streams in the System 573, something that MAME hasn't wanted to touch due to patents.
I highly doubt the newer games will go into MAME anytime soon - partly because they all run Windows XP embedded, and also because they are most likely considered "too new" for inclusion.
Mame is an emulator, correct? It seems out of scope.
These systems still run custom hardware for things like IO, and those parts of the systems are emulate-able.
Getting emulation of said IO chips and whatever seems pretty inline with MAME's mission statement: "MAME's purpose is to preserve decades of software history."
Emulation is an implementation detail. It may be the best approach or it may be abstracted away.