Hi Dimitri - MoI does already have a move/rotate/scale mechanism for 2D curves, it's called the edit frame:
http://moi3d.com/3.0/docs/moi_command_reference11.htm#editframe

The focus in general for MoI is trying to make things primarily using 2D curves so that's also why the focus is on a 2D manipulator as well.

I'd like to add in a 3D manipulator at some point as well, I'm not sure if it will be in for v4 or not though - possibly. It hasn't been a priority as of yet because the primary NURBS modeling strategy doesn't involve doing 3D "point sculpting" like poly modeling does.

- Michael