yes.. just takes some work and reading alot of manpages and trial and error. We've just completed doing a CD which does that and a whole lot more here. SuSE has something they call EvaluationCDs which you burn and tries out their OS without touching the disk. Based on isolinux, afaik.
Shouldn't be too hard to fix something that can boot up a PPC from CD. Linux already does it, debian has bootable CDs for MacPPC.. so one can look at them and then decide what to put on the CD and then look at what to launch at bootup.
A nice tool, but for what purpose? I'd much rather have the OS installed on the machine..