I have a few issues with this for varying reasons. I too have thought many a time of proposing something akin to this but I've always allowed myself some time to sit on this question and ponder some of the immediate probable outcomes.
Let me start off by saying that I think one of the wRHG's attractive factors is its malleability. In the end, it can be anything you want it to be. Having a single centralized canon will be a bit dogmatic. Now, that may be not what you're trying to say here but if not, then what is your question?
Second, there's a lot of conflicts in between multiple canons and I think having the freedom to be able to work around certain aspects of some canons is a very nice one to have. It'd be a fallacy to say that most people are on a similar level of skill here. There may be some who would like to disagree, like Azure, but honestly there's huge gaps in skills between some of our active members and I think there's some people here who wouldn't like to have their own canon bogged down by other people's more poorly written or thought through ones.
I mean, Alphaeus, I did recently contact you about certain issues with your canon and how they were becoming very obtrusive to some to the point where I myself saw myself forced to either circumvent your canon as a whole, or pretend it didn't exist every time I'd come in contact with it. Both of those are really bad options if you think about it and having a single over-arching meta narrative won't be helping out at all there.
Again, I think that having the freedom to choose which aspects of whose canon you wish to incorporate is a very good one to have, especially in a place such as this one where the skill discrepancy can be a bit big sometimes.
Now you may argue that not everyone has to submit to this over arching meta narrative and it could simply be out there for those who would wish it, but I have two issues one. The first is the biggest, being that doing this can create an "us vs them" gap in our community that can go either of two ways ; Either not enough people are interested in this overarching meta narrative and those few who end up embracing it may become increasingly isolated because nobody that's part of it really wants to have much to do with it, which may create situations akin to the one I had with Alphaeus' canon, OR too many people will adopt this meta narrative at which point others may start feeling peer pressured into it. I know this isn't really a peer pressure-esque community (thank God) but that doesn't take away that this meta narrative can become very opressive to the few that wouldn't wish to adopt it.
My second issue with having it being so optional and up in the air is that it'd be utterly redundant. We already see so many people merging their canons up to very severe levels willingly, we see influences from other people's writings and depictions of this universe pop up everywhere and we've already set up some conventions that are near universal anyways.
To list a few ; There seems to be a general consensus that the RHG is both a corporation and a system, the city the RHG is set in (which varies for many people) seems to largely also serve as playground for these battles. We see little interfering from the government in any canon which can lead us to assume that the RHG corporation also owns this city.
Stuff like magic, supernatural occurences, aliens and metahumanism seem to be commonplace and, while often shunned in other places, more welcome in the RHG itself. It seems to be a bit like X-Men where sometimes people are simply born with extraordinary abilities (though we don't refer to them as mutants).
Things like conspiracy-esque organizations are also largely embraced to exist in this universe. These are usually also the ones to supply us with all this funky ultra-technological stuff we have in our stories.
Generally though, as Crank observed, there's simply too many people who make their canons quite big and trying to merge all those together would cause too much conflicts, let alone taking into account all those smaller canons. Too many compromises would have to be made, compromises neither party would be glad with.
So what I'm trying to say is, there's nothing wrong with doing things the way we're doing them now. I get that it's nice to write things down concretely sometimes, but in the end if people want to merge canons they find their own ways and it usually works out for the better, so just let em. This is taking it a bit too big for my tastes.