By doing oscillator swap - have you run any other issues?
Thankfully the biggest issue with everyday operations on a Q700 is just overclocking too much. 33 was my limit before losing features, system stability, but your mileage may vary.
I can't speak to A/UX in
depth. I managed to get version 3 completely installed on mine, however I was unable to keep it running after several bootings due to a degenerative spinning HDD malady. I'll be happy to proven wrong with other examples, as I'm simply one witness.
The Gestalt ID problem is more a concern for 040 Macs where a) board resistors' effects on gestalt and frequency/driver value are interconnected (475/605) and b) where board resistors change the gestalt only, but that in turn changes memory timings from ROM and prevents POSTing or booting at higher frequencies (650/800)
I haven't looked into the 63x/64x Macs, but they appear to follow a derivative process that of the 475/605.
MacKilroy is correct though, that these unused gestalt IDs fail in operations where the system enabler doesn't have those IDs.
The gestalt does not change on a 700, as far as I've used it.