I'm curious why you think a newer version would be easier. The Wii, after all, is from 2006. It used an IBM processor that used what's essentially PowerPC G3, which Apple started using in 1997.
Chances are the commenter you’re responding to threw the “x” after Mac OS as that is the common verbiage for the operating system, not realizing that X represents a version number. I know I’ve made this mistake countless times as well.
I was thinking The X public Beta or 10.0 might be easier because it's BSD, and you can drop into verbose mode and see what's happening.
I had to do some work to get IIRC 10.2 (or maybe 10.3 or 10.4) to boot on my PowerMac G3, but it was doable booting into single user mode and going from there.
Apparently 10.4.11 was the last to support PowerPC without altivecs. I'd imagine that you could rely on the ubiquitousness of open source kernels to figure out what's not booting right considering that you'd need to write all of the drivers for the peripherals.
