The skinning of those plugins is just replacing graphic files, so while interesting, is probably one of the easier things to hack into a firmware most of the time.
To get 3rd party plugins to work would require an API of some sort that could manage Audio In/Audio Out/Midi Data/CV Data/etc...
I'd imagine the easier thing for somebody to hack on would be to try and get the Hype Synth over to the MPC from the force, but that'd assume that it's a real plugin and not just compiled into the Force executable.
The best way to get at this kind of stuff would be with a dev kit, but barring that, it becomes pretty gnarly to start figuring out the build roots for the application, build out library dependencies, replace whatever Akai has created without having docs, etc... It's not to say that it's impossible, but for most people it is far more work than what you'd get out of it in the best circumstances... Even if there is an API interface that could allow third party apps, without a header file to declare what the function calls are, parameters, and returns... it becomes a huge problem to figure out how to map all of these things. Again... it's possible, but it then relies on somebody with serious debugging skills, particularly in the ARM environment, to be able to rip these things apart and understand what they are doing.
I've got a lot (not all) of the necessary background to get into this stuff, but I feel like I have better things to do with my time... like actually make some music
