This can be done, of course. But clock signals are very aggressive and can lead to high ground noise, when being routed across the board. A central clock will always result in much longer clock signal traces, than when using the built-in Pierce oscillators.

Also, why using an external clock, when the micros have one built-in??

A central clock would only make sense to me, when a certain synchronisation between a group of micros is needed.

Kai