Most all the Deere semi-mounted plows I've seen are box-tube framed. They don't lend themselves to reducing size very well, but it can be done. Remove rear bottom, and move steering wheel forward.
Truss-frame plows can be reduced quite easily. Unbolt, and re-assemble....
As Ken Sweet has already said, 3 (relatively scarce) 4, 5, and 6 bottom semi-mounted plows are at less than scrap prices around these parts. (They're a BEAR to move...)
Anything 3 bottom or less...GIVE ME A 3-POINT PLOW!!!!