Nothing is missing :-)
Your PMC8 is built around the Propeller chip that Jerry described, and it is a dedicated real-time processor. I'm not aware of anything else like it on the market. No, it's not a general-purpose chip, but it's a fine choice for what he needed it to do.
On top of that, the motor control functions are encapsulated behind an API (the PMC8's control language). So whatever astronomical control program comes down the road, now or later, just write a driver to talk with that documented API and you're good to go.
So yes, the new purchaser does need to have a separate computer to act as an executive for the PMC8, whether for visual or AP, but IMO that's a feature, not a bug. It preserves independence and versatility. Today I use a Win7 laptop and ASCOM for AP, but when that runs out of gas for me, I'll probably end up with a Raspberry Pi and INDI - based solution. And when someone comes up with yet another astro-gadget-management platform, that will probably work, too - because the PMC8 converses with its control programs but is not entangled with them.
Hope this helps...
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras: Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer: Thinkpad x230, Win7Pro/64