Current Solvespace maintainer here. IMHO there is a lot that can readily be added to solvespace. Then there could be a big effort to do hierarchical sketches. And it is reasonably possible to rewrite some of the geometry internals if needed. All of these things are a LOT of work. The problem is the number of people with the background, software skills, and interest in contributing is very very small.
Having said that, we will just keep chugging along. I've been very busy with personal stuff this year, but soon should have free time to address my backlog of stuff I personally want to do.
Open Source has the advantage of time as long as people stay at it ;-) OTOH Blender and FreeCAD have used the constraint solver. If they borrow some of UI ideas then we all win too!
