Intel supplies most of Apple's CPUs, yes?
Intel supplies all of the CPUs used in Apple's desktop and laptop computers, yes.
Personally, I think Apple should take their cash and make their own processors
Is that "Apple should take their cash and build their own foundries" or "Apple should take their cash and buy an existing foundry"? In either case, it's "Apple should continue to invest in foundries to update to new processes", and, in either case, I'm not sure how easy that would be.
Or is that "Apple should do their own chip designs"? Anandtech suspects they're already doing that.
allowing for their OS to have a firmware component
If by "firmware component" you mean on-chip firmware, how is owning your own foundry, rather than having another foundry fab your design, a requirement for that? Or does this mean that "Apple should take their cash and build their own foundries" means "Apple should do their own chip designs" rather than "Apple should do their own chip fabrication"?
and thereby boosting performance and security.
What sort of firmware customization are you talking about here?