For someone to see it, they need to willingly click on it (even after you have put a disclaimer), download it, have a 3d program installed, have the importer for the 3d program, and know how to use the 3d program, and manually alter mesh data to see the “goods”
There are already 50 times more safeguards there than putting an NSFW tag on the thread and a picture
If the model is wearing clothes on top, how is it different than a “dude with a gun”.
Its not like that thread with the picture of a hippo-monstrosity. You are just posting some 3d model data for analysis and discussion.
Edit: just to add something regarding your request: MMD conversion to GMOD, almost ALWAYS requires the head to be separately split and reattached anyway. Unless the model is really old, MMD models tend to stretch GMOD’s resource limits to the max. So as for your request of having a model go “headless”, it pretty much already happens by default during the process, unless u were trying to convert a pre-2009-ish MMD
The reason we tend to just use the “head that came with it” anyway, is to maintain the author’s original model “integrity” (part of mundane MMD rules), and because other heads are not guaranteed to match the base neck without modifications (costs time)