Yes this type system would be nice for gaming, but another thing I think would be helpful is to provide "solo" objectives for various group missions.
Example: I'm going to use the events in Mass Effect 2's final fight, where you send someone into the tube to open up doors, while the rest of the party fought it out in the main chamber. I think, if they added objectives similar to the "tube thing", where 1 player has to go off and accomplish an objective on their own, to support the larger goal, it might encourage solo players to contribute more.
If you are using the term "solo" player in the strict context of multiplayer games, then I wouldn't be a solo player. I do prefer single player games though, so in that context I would likely be a "solo" player, but if the game allows for team play, I'm a big fan of it. I think the biggest problem with PUG's, and multiplayer in general, is the need for leadership, without necessarily having someone capable of leadership, or a couple of rival alpha-males, arguing over which strategy to take, because they both want to be in charge. I can't count the number of times a group that started out perfectly fine, devolved into a flame war in mere moments because 2 people decided to waste their time and energy on arguing, instead of just playing the game. And those type people are most likely the ones who will be forming these groups that you mention, looking for solos. And those are the type of people that discourage solos from taking part. "Is this group leader going to be a complete asshole and fuckwit? Or is he going to be relatively level headed? If you, as the solo player, are joining other people's groups, you are still going to keep running into this issue. These type players are less likely to start their own groups, because that would imply that they are now in charge, and they don't want to be in charge.
So I like the idea of a rating system for the players, with multiple characteristics to rate them for, as I think, if the information was made public, it could potentially help a lot. It won't fix everything, but definitely a step in the right direction.