I think this function would be super cool.
BlendCrv could offer perfect blend between two curves matching start and end curvatures of blended curves BUT the resulting curve would have curvature linearly changing along its length --> perfectly smooth transition between two curves in 3d space (perfect in the elegancy). It is called euler spiral or clothoid and is not trivial to describe mathematically. I dont know if euler spiral is defined only in 2D space but in 3D should have the same properties.
What do you think? Is it a easy thing to implement?
Sorry for my kids drawing