Hey Norbert, that's a GREAT question!
This reminds me of a naval architecture question i saw elsewhere:
http://www.shipconstructor.com/...m/viewtopic.php?f=2&t=62This one is highly applicable to what i will encounter soon enough, making flanges.
Currently, i've been making a profile of various sizes according to location in the hull. Midbody areas have thicker elements, and the fore and aft areas have thinner but more numerous stiffeners.
My thinking is that for this model, it may have to be broken down into zones or parts that remain (or are highly likely to remain) fixed in general, with the ends being "cut to suit" their terminations.
I was successful getting the cyan area to move (as it appears you did, too) to a more distant or a closer termination against plate and that saved me the work of extending beyond and then the need to trim back.
So, I'm not sure, but it may be that Tim & co would need to add some code to "maintain relative angle of (selected edges between two points (or more points?) but extend or trim distance of (profile edge) selected.
Alternatively, maybe a "stretching/retracting plane" of sorts can pass thru the part at the bounds of what is to remain fixed; everything in on the opposite sides of the boundary plains would be stretched according to either an angle referent or according to an edge that is allowed to move, so maybe the plane would be some infinitesimally small but discreet distance inward so the bottom edge stretched is of neglible length at the beginning of its own stretch.
Not sure if this thinking is making sense, but i'm firing it off before catching my bus.