Todd,
I am using a G3/333/OS 9.2.2 Lombard PB in much the same way you described/envisioned. It is a fine computer and has a built in SCSI port. But to connect via WiFi, it was necessary to get a Farallon (or equivalent) WiFi card for the PC slot. It works great and file sharing with my G4 DP/800/OS 10.2.3 has been a joy.
But, the next model up, the Pismo G3/400 comes with Firewire (instead of the SCSI) and, by some reports, will better accommodate OS X; though many have installed OS X on a Lombard. It’s just one of those machine that is on the “cusp”, so results may vary. Still, I think the Pismo may be the first choice. Unless, SCSI is important.
In my case I have upped the RAM to 384 MB and the HD to an IBM 20 GB. Perhaps that will help as a point of reference/baseline.
Harv