Right now this log only serves as a collection of ideas, here's what I plan as second step:

To control the hardware part, the next step is to build a controller unit.

It will hold a raspberry pi, a RTL-SDR stick, motor driver and software to glue all three together.

RF decoding will be done by a RTL-SDR Stick, radio data will be streamed by a rtl_tcp server running on the pi.

What I want is the controller to accept commands from the hamlib rotctl client. Therefore I'll be writing a python script listening to incoming tcp connections, rotctl_server.py (which will be avilable sometimes later under the file section of this project).
This script then will call out via serial terminal to a controller-board (some arduino or PIC controller) which subsequently talks to some A4988 boards. I recently had the fortune working with these A4988's for another project and I like them, so they will be my first choice.
They are able to deliver a decent current to stepper motors and allow for microstepping. And they are cheap.
The dedicated driver board will support emergency-stop-, position- and end-switches for safety reasons. I don't want to damage the device, me or someone else because I made a mistake in programming.