Unfortunately MAME on AGA and 680x0 is very slow. Even with manual tweakings in the source code it is still slow. There are some individual arcade emulators that run better, but they are not as good as MAME. Putting exec library patch and BlazeWCP will help a bit, but not much.
Now that AmiMasterGear sourcecode is available, one may take it and use it for the Z80 based MAME games, but it wil be a lot of work to make these games work. Games like Hang On Junior will work perfectly with the AmiMasterGear engine.
Certainlly, i hope somebody with enough skills could implement the AmiMasterGear Z80 core emulation on a new MAME bootleg, that would allow us to play some z80 based arcade games even on a modest 030 /50.
However i guess it could be more reasonable to aim for a new release on MorphOS or OS4, or even on the NatAmi whenever the project is finished.