Hi
I really like this idea and I agree with @majken that getting support from the product teams is vital. They often have roadmaps already in place for future releases, but they may find this process useful for a) helping to prioritise and b) for new ideas that are currently off the plan.
I also agree with point made by @yoric that it would get the community more involved. If you think of the vouched Mozillian community as “super users” we are in a good place to help guide Mozilla software development. Just think of the range of possible areas from coding to GUI that contributors could have ideas in relation to.
Let us not get too carried away though. The idea of a trial process makes a lot of sense, but I would suggest that it is limited to one product (for example Firefox for Android) so that the trial can work with, and get feedback from, one product team. This will give good feedback to either build on this for a possible wider role out. As with any good idea, people need to appreciate that this channel/forum/thing may not work - failure is not bad, it just means people need to find a different approach.
As someone that is a member of the vouched Mozillian community and has no coding skills, but who has experience of pitching good ideas in a non IT setting, I may be willing to help wrangle this, however, I would need to hold fire on doing anything until mid-May at the earliest due to other (non Mozilla/SUMO) volunteering commitments.