> engineers with the low-level experience probably are way harder to find than for ARM

Eh, the instruction set doesn't matter that much for modern CPU designers (within reason). Apple's in house expertise came (in part) from their acquisition of P.A. Semi and their PowerPC engineers; Apple it seems immediately redirected them to working on ARM designs. And the Transmeta guys proved that a third party can put out an interesting x86 chip if you can get access to the licenses.