What does make an initiative that your proposed to be compelling for users to participate in?
Tl;dr; To be active in an initiative users must see a personal value in the initiative and feel that its end result is valued by general public.
A required condition to make volunteers engaged in anything is that they should clearly see that their contribution is valued by those they help, as well as by the community at large. If you want to engage users in a collaborative activity, the outcome of the initiative must be valued by everyone involved, including those who get the value from the end result and those who participate in the activity.
This is a fragment of a draft of the book “Lessons Learned While Working On Stack Overflow”. Read the full book on kindle or the paperback version.