I see that you have constraints on your roadmap, but that's not what I mean. I am specifically referring to the 2D mode of Vectorworks, which is, special modules aside, really just a vector editor with support for hairlines and representational line styling (so lines don't have a 'real' thickness, but you set semantical pen thickness).
The main feature here is more about the path drawing workflow, which enables you to efficiently work with exact measurements. E.g. to draw a line you'd click to start, hover on the desired angle, enter number, (optionally press tab, enter exact angle,) click. A rectangle, say, would have additional parameters to access via tab.
So thinking about it, it in fact it is kind of a restraints system, but it only applies to the current drawing process and has the absolute minimum needed key presses/actions as possible, because you need to do this a lot (Sketchup works simlar, too)
I could see myself working on something like that, but didn't see anything pointing in that direction in your open tasks, so I am wondering if that would be in scope for graphite.