Yes, they are a real pain in the neck. I dont know what to do against them. Block them, yes, I always check the "disconnected X times" entry in their stats, but a pro knows how to keep his record clean. Sometimes ppl only got a CTD, you can't distinguish if the guy's a quitter or crashed.
A good indicator who will be a quitter is who posts "gogogo" and got little patience for the slots to fill up. My usual habit: gogogo = kick! More gogogo=block
Hosting smaller games myself I also noticed that quite a lot it's the veteran players who quit as soon as they see their tactic doesnt work or their teammates waste material. Lower ranks usually quit when all their ressource points are gone. To counter that you can set the manpower high, so the noob can waste and waste and waste and still got something to waste.
Quitters ruin up to 15 ppl's game. I thought about sorting them, ppl who quit, ppl who quit but at least say they'll quit, ppl who suddenly got other things to do and hand-over their assets to their teammates. But it's far too much work.
A key problem in MoWAS: players dont communicate, very seldom cooperate or stay for a debriefing. It's an ego-game. Sometimes there is a highlight: Communicative players before the game starts, lot's of in-game chatter, tactical thinking, comradeship and a friendly after-game discussion. It doesn't matter if the game was lost or won.
You are not alone with that common problem
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