Some people claim drawbar organs are not really organs There are some Hammond drawbar simulators out there but they require a different philosophy from a pipe organ. The Hammond is based on a few stops, mostly flues, whose volume and percussiveness are modified in real time. Hauptwerk is not built to interpret this data. The physical equivalent would be ranks of flues that put each rank under individually constrolled expression and modify the wind pressure for each rank on demand. Better done with something other than Hauptwerk.
I tried to take an old drawbar console and MIDIfy it but the drawbars and keyboards were very difficult to work with and there are some Hammond MIDI controllers available.
Thomas