@wiiant the real question is if there are any ARM specific optimisations for the pi that would lend any benefit over the current vice emulator or if due to the lack of processing power of the pi it would run like cold tar in attempting cycle accuracy ;)
looks the source is available, but will require basic compilation knowledge and even more retropie specific knowledge to turn it into a module for retropie. I don't really have time to look into it but there are guides online for compiling under Linux and there probably is a specific guide for compilation on the emulator site or readme