SJ:
We've encountered a few, and have entire chapters of process on how to handle them. You'd rather filter them out in advance, according to some set of profiles?
By defining the purpose of our site and community and adhering to it, yes.
post-discovery discouragement may no longer work, because these users have their Wikigames ghetto to return to and come back from, where rules like NPOV are as relevant as Schopenhauer is to the Furry fandom.
You think this is different from the "Child-love article cluster" ghetto?
Absolutely, for the reasons I have given. The child-love article cluster is a part of Wikipedia proper, and many people are working on it to try to make it NPOV. If you can cite a cluster of articles that is fundamentally out of sync with our key policies and purpose, I'll be interested.
Let's wait until we actually have a problem -- say, more than 10% of game-playing users who are not also active wiki contributors or newbies
10% of active users? You want hundreds of people playing games and doing nothing else before you consider intervening? Absolutely no way. For the reasons I cited, late intervention is not an option -- particularly since those 10% will then become vocal opponents of any such intervention, citing precedent and lack of consensus. The problem needs to be stopped at its very root now. You have presented no single plausible argument why this is not so.
Erik