This is a good suggestion, and we will consider how to integrate this and make it easier. However, by way of explanation, I want to clarify why the system behaves the way it does.
When we first implemented support for models, we found that many of the models we got from public marketplaces like TurboSquid, would have model points that were nowhere near the FBX origin. We’d find models that had points several hundred or thousand units away from the origin. There appeared to be no rhyme or reason to where the content was “centered” or placed in the FBX coordinate space.
So we felt it would make more sense to novice users if we simply snapped to center (of the points of the meshes of the FBX).
Supporting the origin being an assumed point in the mesh point cloud, and setting the “registration point” to be the origin of the FBX would be possible to do, although I don’t think it would make sense to do that by default (based on the models I’ve seen out in the wild… most model artists appear to not use this approach).
There would still be some challenges… that might cause moving a single point to still distort your model in world… namely if you moved a point so that it was outside of the bounding box of the union of all mesh points. This would cause us to “resize to fit”. But if your model editing was always within the bounds of the the existing mesh, you’d get the behavior you wanted.
Anyway… we will think about this more and add this to our product backlog, and see if/when/how we can slot it in based on other projects.