Unless you're lucky enough to find someone who's already done it, I'd not think you'd want to venture there. It could be done, but would take an enormous amount of planning as the relationships could get pretty complex. This, coming from a guy who wants to do most everything with Filemaker.
SheepSaver is a utility that allows OS9 applications to run in leopard and intel macs.
It is not easy.
I've constructed a good working FM database for Genealogy use. Originally it was for dogs but I've removed all the inbreading calculations and judges protocol's and stuff. Sorry no GEDCOM conversion yet, but that file-format is so antique....
(As you can see from some of the buttons I started this project in 1999 with FM 3.0.. :-)