wow, I think that pretty much covers it, just when I was thinking of attempting a response...
There is one issue that should be dealt with soon, namely whether to render curves as splines or as many (tiny) connected multilines. The splines are more pleasing because they are reversible (lossless). On the other hand, for CNC machines the multilines are sometimes mandatory. If this were done it would have to be done as an option because both classes of users will have strong preferences on this issue. The other available dxf routines, I believe, have focused on the CNC multiline approach, while the Cutting Plotter routine has deliberately not gone that route. (Also, Inkscape has a Python routine Modify Path->Flattern Beziers that can already do this conversion.) Anyways, perhaps one of the other routines could be chosen to do the multiline CNC approach, or alternatively, I would be willing to add it in as an option to the Cutting Plotter routine. If I did, then I would probably do it precisely the same as the hpgl output was done.