IMHO, it does not make sense to optimise for a particular CPU in a particular machine (e.g. G4 in an original AmigaOne), because in general you will gain *very* little from it, but you will end-up with an executable(s) that almost no-one can use. IMHO it only makes sense to optimise for a particular CPU (or better, a CPU *feature*, e.g. AltiVec) when you will gain a significant speed advantage (e.g. 1/3 or more).
It always annoyed me when there were executables compiled for '000, '020, '030, '040 & '060, because I suspect that most of them performed (virtually) no different than any other, so they just wasted disk space & caused confusion. I especially suspect that the '020, '030 & '040 versions were virtually identical, such that you could get rid of the '030 & '040 versions without any problem. (The '000 is needed for compatibility with the oldest machines, while the '020 added cache support (rather important to not kill performance), and the '060 lost some instructions (and significantly differed in other aspects) thus making it somewhat incompatible anyway.)
The X1000's CPU already runs generic PPC executables very fast, so I don't really see the need for creating a special executable (except for AltiVec).