I have made a few diamond frame stools in the past,
Similar "stool" can easily be adapted to be used as a seatpost holder/extender for the Scorpion frame, just simple weld of a base plate to be bolted onto the frame.
Just trying to find some scrap frames from local bike shop is taking some time during the height of cycling season.

4 bolts on the seat secure the seat to the frame, circled in orange.