Thanks. I did not consider a track ball. And I would not want to sacrifice one thumb cluster for a track ball on my keyboard. That means it would need to be modular (like pull out thumb cluster, insert trackball). I consider two track points though.
Group buy: Based on the responses, I think I could find at most few hundred users for this at about 200-300€ for a piece. That is highly unlikely to pay for the expenses. I'll see. Maybe I'll be able to get a cheap access to something which would allow a group buy. Till that time it is only for people who are able to built it themselves (the design files are available).
