This isn't really an MMU design, then. Still very cool, though! FYI, MMU designs have multiple parts for separate extruder assignments in slic3r, no modifiers needed. The best way to preserve them is using a different format, like AMF instead of multiple STLs. Here's an example of mine: https://www.thingiverse.com/thing:3357009
Thanks again for this clever design. I might try printing it in HIPS.