Having a layer based display order system might partially work. I can imagine another column in the layer settings, like the intersection group number, where you could order all your layers by expected height from top down.
The trouble is this would only half solve the problem. ArchiCAD should know how high something is with respect to something else, and automatically display accordingly.
It would be best if ArchiCAD actually used a real height-based display order. The problem only arises because the floorplan is a symbolic view of what is actually happening so there are situations where no amount of fiddling with the display order will work.
Imagine two intersecting 'C' shaped roofs, for example, each with parts overhanging the other. It is impossible to get this to display properly with the correct bits of roof correctly obscuring the other at the moment, without extra 2d work.
So I say implement a true height-based display order system, and leave the current draworder tools to get 2d fills, lines and text to display as you need. Anything else just wont solve the fundamental problem.