I just noticed your post in the Extension Development forum LB so i will have to try this soon as it seems like a great idea.
The idea of new dialogs for extensions is great also, it worked with XLua and other extensions so i think with MMF3 if a SDK to extend the actual program dialogs happens that takes what can be done to the next level. If as well as new extensions to download we then new have tools and editing dialogs also that would be really cool i think. The next extension SDK can also extend on this type of thing and i think it's really great to see devs sharing resources and this happening already with MMF2.