Autodesk needs to fix the errant limitation on copying and pasting sketch lines, Model Lines, etc. across family types and across projects and families. It is extremely annoying and has no mathematical basis for existing: These entities have a relative xyz coordinate space and so does every other template and project space. It's an imaginary limitation that makes Revit look dumb - which it is in this case. Unless, Autodesk comes to rescue and fixes this glitch. Thanks.
Example of Bad Coordinate Space Mathematics in Revit