Frank, would this not address every mount?
1.When using SGP centering, be sure your mount model is cleared (no mount model).
2.SGP does not send SYNC to mount when centering.
I'm not sure what you're asking - but the approach I describe should work for any mount and I'm not aware of any problem with centering reported in this forum that would stop my suggested method from working well.
As for your point 1 - it would not matter if your mount has a model or not. It just needs to have pointing accuracy adequate for a good plate solve - but that is already true of the existing centering method.
And for point 2 - my method would not require a sync - but it could be done as an option at the beginning and/or end of the centering routine.
Frank