There are many characters that never got any canon depictions, and I think running MoC and/or art competitions to represent some of them would be a great way to help keep the community together and active. MoC competitions don't get as much attention as they used to, but having the winners become canon representations would certainly generate interest!
So, would you be okay with doing any such canonization? I imagine these as potentially being very much like the competition for Certavus, the legendary Ice Glatorian, i.e. MoC competitions with some artwork based on the winning MoC.
From what I understand of your position on similar issues (correct me if I’m wrong), characters with important, unestablished details (such as the Kanohi and Toa Tool they use) wouldn't be viable, since those are story-relevant details that you would be reluctant to let fans decide. However, there are other characters, such as Lariska the Dark Hunter, Varian the Toa of Psionics, or even some of the named Great Beings (arguably), who already have their core appearance details defined.