This topic is certainly... charged.
Fun fact, I'm actually against the idea of Canonization contests as a whole - I think they resulted in both some of the coolest, and absolute dumbest parts of Bionicle G1. That being said, I'm going to echo the sentiments given by Eljay and Ghid, namely what do we have to lose?
For people concerned about the Custom Piece economy - my question to you is exactly how will this affect it? People aren't going to suddenly want to pay hundreds of dollars for a 3D printed mask just because Greg/the Community say it's Canon. And Lego, for what it's worth, isn't involved in this in any proper way. These contests are, at their heart, "suggest Ideas to the author" and I don't see how that's necessarily a bad thing. Similarly with the issues of people ripping off designs - I truly believe that it is NOT our place to police this. Shapeways and the community as a whole have the resources to keep this in check, seriously, It will NOT take that long to name every Bionicle Modeller who has the skills to enter something into these contests and win. Failure to use the resources afforded by Shapeways/the Community is NOT a failing of the contest.
While I can sympathize from an accessibility standpoint, which is to say "people with less money will have less ability to get cool parts with which to win these contests" I ask how that's any different than the situation we live in now? People with more money can buy more of the now-limited supply.
For people concerned about the idea of these contests 'stepping on toes" my question for you becomes, "What about the people who designed Toa Jaller and Toa Hahli years before the Inika were a thing?" If we base what's true to the story on a collective interpretation, we're only solving some of the issues that caused Bionicle to die in the first place - namely, that there's too much going on and too much of it is barely explored. RSG is making it their mission to create a fanon for the Matoran Civil War, and I guarantee there are people out there who are feeling stepped ALL over based on a group of fans setting out to depict every mask ever mentioned.
More to the point, 3D modelling has become a HUGE aspect of how this fandom stays alive. To completely write off an artistic expression because of fear of knockoffs or people being angry is kind of a weird notion. Like, what happens if an artist WANTS their model that's now "canon" to one type of obscure mask because the community voted to be free anyways?
In essence, my understanding of these contests is that Greg will consider what is depicted Canon. Not that it's suddenly the be all end all for the community, but that the writer will consider these canon.
For a dead storyline, specifically g1.
What a lot of this speculation occurring right now, in a poll asking if there SHOULD be contests in the first place, is literally people jumping the gun and freaking out before ANYTHING has been decided or even really considered. To come out of the gate before ANYTHING is known for sure saying that we should outright ban xyz or that you'll not allow xyz is the kind of thing that can be figured out once an actual FORMAT for these actually gets worked on.
These might all be complete non-issues. I vote yes, and bring the pitchforks out later. Freaking out over what might happen is a useless endeavor when the question is should we look into Canon contests in the first place.