So long as a machine passes the tech-check and behaves in a predictable manner I can't see any difference - although it does sound a little like overkill if I'm honest. There are plenty of machines that run a custom-programmed PIC alongside the PIC that might exist on their speed controller for example, in fact it's something we're looking into at the moment.

Having said that, I wouldn't advocate making anything more complex than it needs to be, and there are plenty of off-the-shelf controllers that will do positional feedback and/or end stops. Never a fan of re-inventing the wheel when a cheap, reliable, off the shelf commodity product is out there that does the job