Our tandem is equipped with a Shimano GRX 600/810. That works fine, I'm happy with it, however, I'd like to change to 12 speed to get a broader range of gears, which is important for a tandem. To safe money I'd like to keep the front front derailleur and just add an DI2 827 rear derailleur, together with a new right break lever of course. So the left side would stay mechanic, the right side electronic. Would this work?

If not, would it be possible to change the GRX 600/810 mechanic components for the rear derailleur with mechanic 610/820 components?