Theres some good app info, thanks.
>>
I think we can allready forget the interactive sweep stuff. I just did a quick test in MoI, interactively change some curve's control points after a sweep (a simple circle as root shape) is allready really slow, and I 'only' have 10 control points on the sweep rail (and I use an angle 35° in the meshing angle option to speed up the process)

So 'just' the OnSurf offset option would be enough :P
>>

Yes, seperating out the onsurf offset suggestion, here I agree

(this is just me expounding on the interactive idea)
That makes sense, however, extrude seems fairly instantanious. Am wondering about "continuous extrude" where keep picking as you go??? Then also to expand here, the continuous extrude with the curve tool as opposed to the polyline tool, that doesnt create a "break" at each chosen point?

Make sense?

I think the slow part above is due to the recalculation of the entire obect when done that way. When done while drawing, theres much less going on "per pick" so it seems more like click, click, click.. instead of click wait.... click wait....!