Cheers for the vote of confidence Rooster
IStonia: Wings Circularise
does indeed flatten it to a plane. I tried to make a more extreme example for you. You can see that it doesn't flatten it a particular world plane so I leave that up to you to decide how to best implement.
I think Wings does a pretty good job of sorting out this
The Curve loop
works brilliantly so far. Nice one
With regards to hiding the geometry to isolate the operation I'm not sure this would flow well. As a modelling function I think making intricate selections to hide components and then perform the function will hamper workflow (especially if the scene is complex). Also, as an artist 1st, I need to be able to constantly see the area I'm working on in relation to the rest of the mesh. Hiding will disrupt this. Maybe it will be intuitive after having some hands on time.
As a final addendum (and in defense of the Endloop Marker idea) I would probably never use Curve loop in Polygon mode, Mostly in Edge mode and occasionally in Vertex mode.
Maybe we need other Polycount members to give their feedback but this is the way I would personally prefer to work. Continuously making selections then performing the function.
Space Loop currently doesn't behave correctly at the moment.
Need to test this a bit further as it completely mangled a mesh earlier but it's working correctly now.
Just noticed a BUG
with 'loop select' button in edge mode.
With an open mesh if you double click on an open edge it will select the ring but if you single select an open edge and choose 'Loop Select' the operation doesn't work.