You can't combine controllers. But you can interface different types to the computer. Here is an example of an interface that can easily be put together, regardless of whether the rotor controller has a dedicated interface jack. This is from a post I made last month to similar question.
A good place for information on rotor controllers/interfaces is the satellite tracking programs listed on the www.amsat.org
website. Look in the documentation for each controller
The NOVA program has information on a very simple solution that uses a commercial multipurpose USB interface box, you then build a small board with the TTL components which can connect directly to Icom control port. Once you look at the circuit it is simple to modify it for other brands of rotors with or without control ports. **Note, the Labjack U12 has both USB & Serial DB25 interfaces.
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The Piggyback could easily be made up on perfboard. The IC chip costs about 65 Cents. I have one of these!
Bos Ebal Nolom! "South African Cows on a mountain in the West Bank!"