Could be a good idea to have a look at the NetBSD for initialization purposies and hw interface. BTW, if you do not plan to use the MMU (by far, a complicated task), could be a good idea to target the A500 or A600. A lees complicated processor. Try to use UAE to run your soft, that will save you plenty of time ;-)
As was already demostrated several times, a modern kernel can be done by one person. A modern OS is a bit more than a kernel. But a working shell should be your safe bet milestone.
