Could you devise some kind of fixed, toothed interface to "grab" the chain at one side of the Powerlock, and a similar set-up to "grab" into the chain at the other side, then, at one end, use some kind of rotating leverage arm, held in place, perhaps, by the frame of bicycle and allowed to turn freely by utilising a set of bearings, and attached with bolts to the toothed interface, to apply a relatively large force to the Powerlock, in order to snap it closed?
It would be easier with some kind of handle on the end of the arm to improve the ergonomics; you could even try incorporating a perpendicular rotating platform to the afformentioned arm and use your foot to operate it.
Just an idea…