I am very glad this is being discussed!
Here are my opinions from what I've been able to do thus far using Inkscape and my vinyl cutters:
I would not bother with any format other than HPGL. It is a standard for desktop and large format cutting plotters - not just Graphtec. (Graphtec has some proprietary formats, as do others...)
I have a 15 year old 24" Roland plotter and a less than week old Graphtec 48" plotter ( vinyl cutters ).
The exact same file can be cut by both machines with no alterations other than the original setup. Graphtec defaults to it's own version - GP-GL, this needs changed on the control panel to standard HP-GL.
What I do right now is: 1. Make the drawing in Inkscape 2. Copy what needs cut to the clipboard 3. Open a new file in Inkscape 4. Paste clipboard data into new file 5. SHIFT+CTRL+D to access properties of new file 6. Click the "Fit page to selection" button 7. Save file as "newplot.ps" 8. in terminal, enter: ./graphtec.sh < newplot.ps 9. plotter starts and cuts perfectly, absolutely ignorant it is being controlled by open source software!
The file 'graphtec.sh' is a modified version of a script found at: http://www.3x6.nl/inkscape_hpgl/....html
It uses hpgl-distiller - a program that can be downloaded from: http://pldaniels.com/hpgl-distiller
This sounds complicated, but once it is set up, it isn't much worse than any other vinyl cutting software. I've used plenty of them!
I will gladly help actively work on and test this. I also have plenty of other ideas to help inkscape become a full featured vinyl cutting solution.