@motomo I've been thinking over the 6HC vs the Duet 2, and I think it would be possible - although I have not checked all of the input and output requirements. Some things to think about
To control the extruder DC motor, you'll likely need to add a Duet 1XD board to control the Geckodrive G320x (or some other equivalent device of your choosing). The 1XD will send the Step and Direction outputs to the Geckodrive, which in turn will pass information off to the Stratasys PDB (and then in turn, based on the wiring, I believe to the PDB's STMicroelectronics L298 Full Bridge, maybe @AJ-Quick can correct me on that). You may want to investigate power supply requirements, the Duet 6HC can take 12-48v input (depending on the hardware revision), whereas the uPrint has 5v, 12v and 24v power supplies.