Hi Danny, yup that is possible with the geometry library tools. The bigger issue can sometimes be about setting up the UI for such things.
> In it's simplest form you pick a surface and it creates an
> untrimmed copy of the original surface, which would be
> one thing.
This part you can actually do right now by using the "untrim" operation in MoI. To do an untrim, select all the edges that make up a trimming boundary and hit Delete, that will remove that boundary and recover the underlying surface.
The edges must not be a joined edge between 2 surfaces though, so you may need to delete some surfaces or use Edit/Separate on any joined surfaces to break the edges you want to remove to not be connected to other things.
Also if the trim boundary touches the seam edge of a closed surface, the seam edge is part of the boundary and should be selected too.
The easiest way to remove everything is to use Edit/Separate to make the surface into a single unjoined surface, and then select one edge and then hit Ctrl+A to select all edges and then Delete.
Check out this previous post for an illustration on untrim:
http://moi3d.com/forum/index.php?webtag=MOI&msg=444.4
(EDIT: I just saw on another recent message that you definitely knew all about this - are you asking for something different with this extend mode than what can already be done with "untrim" / delete trim edges ?)
> In it's advanced form once you pick a surface, an untrimmed
> copy is created but then you have U and V sliders to enlarge
> or shrink that copied surface.
This one I'd need to think about the UI for a bit which may take some time... Probably it could go in the Extend command, but then when it goes there it may be good for it to have several modes like an "extend to boundary" mode like the regular curve extend.
- Michael