TM compatible AK's use version 3 gearboxes. You'd not have problems with the gearbox putting strain on the plastic, because everything from the motor to the air nozzle, including the main spring, is held in and/or fixed to the gearbox shell. Where I expect you would have problems is getting an AEG hop unit to fit in place properly so that it i) accepts BB's from the mag and ii) allows the air nozzle to make a good seal with the hop rubber.
I wouldn't bother, but if you do, I'd be interested to know how it goes so please take pics of the original, the ongoing mods and the finished article.