I have decided I need to sort of ease into it. So could I use my SASC compiler on MOS hardware temporarily?
You can, but of course SAS/C will generate m68k code, which will be ran under transparent emulation, so you won't get the full PPC speed (but something like virtual 68060 running at 200 - 500 MHz depending on the real computing power of the PowerPC processor in the machine).
What about the SASC debugger (CodeProbe, CPR)? Does it work under MOS? How about the breakpoints and graphical single stepping thru the source code?
I guess you should ask kiero ("kiero" on #morphos at irc.freenode.net). AFAIK he uses SAS/C on MorphOS for compiling 68k programs.