greenmorpher hat geschrieben:a) A grid so we can see what is lining up where.
You could use guidelines or the (alignment) grid in the main window so you can see what the
_result_ is lining up to.
You might even use a vector / outline layer to mark the desired horizontal / vertical references in the original.
greenmorpher hat geschrieben:b) Thinner lines so they can be placed with more accuracy.
Just zoom in / out in the preview window to get the required accuracy.
greenmorpher hat geschrieben:c) It should be possible to constrain movement.
Agreed.
greenmorpher hat geschrieben:d) There should be a read out available so we can add a final tweak to the positions of points and angles of lines by entering a number, and we can have a record of the adjustment made (by manually recording the figures).
Is this just academic or do you have a real world example?
greenmorpher hat geschrieben:e) It should work in the main window as the crop tool does (the bigger the image we are adjusting, the better -- it means we can do finer adjustments).
Absolutely not. You need to see both he original and the preview. Use the zoom function in the preview window and / or resize the preview window as required.
With the rectify tool you define which (imaginary) lines in the original should be horizontal/vertical in the result - this is not the same as the skewing function of the crop tool. I cannot think of a better way to achive this than with this tool in it's current modus operandi.
(Sorry for my poor English; I'm a Swabian, so even my German isn't quite German)