> I think mech games should be left out as I always looked at them as a nusance.
Left out from what? Source code, binary?
The point is to make compiler "front-end", which would be easy to use, as easy is to configure MAME at run-time, possibly simpler.
Linux kernel does it with a simple console script where all you have to do is just check or uncheck some check-boxes and press [compile] button. Don't wanna mech, neo-geo or MESS, uncheck the box! Simple as that.
Then you do not care about what is in the source tree, you simply make your own build with or without any feature you want or do not want. The end, eh?