I think it would be good to have a news post on the homepage asking people to hold off from marking their missions with (please beta test). Any other opinions on this?
I agree completely on this.
Regarding the questions by Laggy, I do agree with marking missions are addon free, however marking them in the topic title will clutter the forum like the situation showed above my post by mathias_eichinger.
However, do not stay away from missions with addons just because of that. Many missions use addons because they bring something extra with them, something you don't really have with vanilla ArmA.
Regarding question #2 I think you should really state that in your topic, that is it SP-able. Don't really know if you already did that, didn't have time to check it out. Also, yes it is much harder to review in a MP environment, much due to the known constraints it all involves (finding players, a server, a timezone, etc etc). But we are getting there.
One thing you can do, if you have a server or a clan, is to call some players to beta-test it with you. If you don't have it, you can tell a friend with a server about OFPEC and he can become a beta-tester himself
with a own server. Wouldn't that be cool eh?