My comment is going to repeat a bunch of what I have read above with a little twist.
I agree whole heartedly that it is the player first and FPS second which dictate the safety of an engagement. However, in the end FPS trumps all as someone will find it very difficult to be dangerous with a 30 fps rifle. Given the type of players prevalent in Canadian airsoft these days I would go after what you CAN control which is velocity limits.
With CQB games I see no need at all to go over 300 fps or use full auto. The accuracy difference is nearly negligible over short distances and I've seen teeth lost on guns shooting under 300 at distances of 30 ft. The only reason I see to accept 320 fps is that there are now many more 'stock' guns which shoot over 300 and I do not believe that the 20 fps is worth having new players downgrade their weapons.
Upgraded guns frankly do nothing but make a player more dangerous until proven otherwise. Of the 100 - 200 players I've met who CLAIM to be mature, safe and awesome ninjas MAYBE 30 of them should have the privilege to carry upgraded gear.
I would vote 320 fps limit, single only, face protection optional.
Oh - and mercies, but that's just because I'm one of those 'pussies' mercies are designed for.
Just as important as above:
Whatever limit you choose, CHRONO all guns!!