@Tom any chance of allowing links to Construct 2 games on the arcade, like e.g. html5games.com does? You have title, icon/image, description, and when you click Play it goes to the site where it's hosted (my own site, or some other portal (Kongregate?) ) - opening a new tab / window. I think this would still help promote Construct 2, even though the links are pointing outside of Scirra's domain.
Having games "published" in some thread (btw didn't we have the "Your Creations" forum for that?), they will get "lost" quickly.
You could even allow rating of those games (like html5games.com does).