Here is my proposal (have made it read-only for now, I can/will allow people as editors as needed)
Regarding the requested amount. My wish would be to work on this with at least 2 other developers that work roughly full-time for at least 3 months. I will donate my time. I could give ~1 day/week from September on, less if we start before.
Looking forward to your feedback, thanks a lot! ivo