Finally, the Gpredict 1.0 beta 2 release has come together, featuring a completely rewritten radio controller / Doppler tuning algorithm. It became a bit more complicated than I originally anticipated, because the incoming requests for improvement of the original controller did not limit themselves to controlling the downlink and the uplink, but also called for using two different radios.
Given that there are very few full-duplex radios out there designed for satellite communications and that they are very expensive, I found this request to be very reasonable and decided to implement it. The resulting controller should be able to work using receivers, transmitters, half-duplex transceivers, and combination of those. Full-duplex has not been implemented, because I am not sure whether hamlib is able to do that properly. That will be implemented in one of the upcoming betas.
The new radio control UI. See more screenshots.