you could try using 3D lines
Yep, this would be ideal.
The only problem is, as you say I have to do 2 renders, and there would be no easy way to 'choose' which lines to draw (eg don't draw ones behind objects and only ones that are along front+back facing triangles).
This sort of thing is fine in C++ or whatever because we have access to the directx functions and can render whatever, whenever we chose. But we only get limited options with this kind of thing in Blitz because it's all done for us. . .
Please, someone - tell me I'm wrong because I would love to make this as easy and fast as possible :O)