I looked for a real 2D-Software and found LibreCAD. After some testing I'm very impressed about the performance and capabilities. My suggestions for the next steps are:
Renewing of the icons. The actual icons with this poison green make LibreCAD look like a toy.
Antialiasing in the viewport would give LibreCAD a more professional look (and will be better for the eyes of the users).
I'm willing to help if someone shows me the way to the workshop.