Modding a speedcube into a shapemod is maybe not the best idear...
You could make a fast Trajber's Octahedron or...
a pillowed speed 3x3x2.
That's not the problem, the thing is the zhanchi as rounded corners and centers, and other things and modding it into different shape could end into something difficult to do, at least to get a nice finish. What I mean, is modding it may affect the inner structure?
All mods are difficult in their own way. ZhanChi mods will, if truncated deep enough, expose a bit of mechanism or cause 'olzing', just as a V-Cube 7 (see Tony's V7 Barrel) or an Ayi 5x5x4 would (see Triaphum's 554 mods). A ZhanChi truncation could create interesting patterns on the surfaces of the puzzle, as in the examples mentioned above. Some truncations cause turning problems, as in Tony's 5x5x5 Cuboctahedron, and that's a risk that must be taken.
If I was in the position of either modding or selling a cheap puzzle, I would mod it even just for the practice.