Just to put in my $0.02 as someone who played here fora while and has since pretty much disappeared:
I think what needs to be figured out is just what type of site vdip wants to be. Because they seem slightly incompatible at the moment. There's the arguments for looser restrictions in order to get more people and more games going. Which is great, however, the more you let people come in and just do whatever, the more likely you are to have your dedicated players become disillusioned with the site and disappear. As Ruffhaus noted, there's already a perception that play on vdip is not exactly "high quality" and that people don't take their games seriously. Allowing people to play lots of games at once (especially with short phase lengths) does nothing to change this perception. You tend to get people who are interested in Diplomacy as a fad, who come in, enter lots of games, and quit when things either don't go their way or they get bored. This leads to a constant cycle where eventually, the top players don't want to play with new players for fear of the game being ruined mid-way through. I know that's been a discussion around these parts in the recent past as well.
On the other hand, there's the argument for restricting play (through RR) which punishes people who don't take the game seriously. While this undoubtedly will hinder the growth of the site, and the number of games played, it will probably keep the dedicated players happier. The people who end up sticking around will tend to be those who finish their games and see things through. This is without question, a good thing. The entire Diplomacy community would benefit from people sticking with things and not just walking away at the first sign of trouble. Is it worth the risk of alienating new players to get this though?
Again, it all boils down to what you think Diplomacy should be. If you think it should be about in-depth strategic decisions, learning from past games, and fighting to the bitter end, then you should support having more restrictions on people who flake out on games so that those who are willing to learn and stick through tough spots become the core of the community. If you feel Diplomacy should be about having a good time, and since it's just a game, it's no big deal if people walk away every now and then so let's just have some fun, then loosening the restrictions so more people can play is undoubtedly the answer for you.
For what it's worth, I'm obviously in the camp of more in-depth Diplomacy as the way to go. I understand you need new people in order to replenish the hobby, but even in my few years of playing, I've noticed that the vast majority of people play a surface game of Diplomacy. "Dot grabbers" as they're sometimes called, don't bother to look under the surface of the game, which is where the real fun is. Sure, it's great to see your empire grow, but the real joy of this game is seeing your plan come to fruition when noone even knows it's your plan, or crippling the enemy plan with words instead of fighting, and seeing their game crumble. Diplomacy is supposed to be about just that - Diplomacy. Unfortunately, it seems to have become more of a tactical game in many people's minds, and the diplomatic part is left out, or seen as an after-thought. I think it'd be wise to implement whatever policies are needed to get people to realize that Diplomacy is the key factory in this game.