Clone

There could be a clone copy of an object that does not need to be a block. When changing the geometry of one, the other linked object would automatically update.

Most probably it could not be as well as not in nearest future.

Currently, LibreCAD does not support linked objects (as you've mentioned, or, say, dimension related to specific entity) and support of such linked objects requires lots' of development efforts.

So may be one day in the future, yet not too soon.

Can we start with vertices, like intersections, tangent points?

They are expensive to calculate and only change with geometry changes.

Also, we can keep them in indexing containers, so fast to look up, if we have millions of points.