So then, who will you be using for escrowing that amount? You should only start this thread after you get the confirmation from the escrow that he has the control of the funds.
I do not agree with you at this point. If someone wants to join the campaign, he need to ask me for escrow. He can make a proposal for this escrow.
I will then send the coins for this user for one week to the escrow (0.05 BTC). As soon as the escrow confirms that the coins are arrived, the user can insert the signature.
Well no thats not the way it works. Just because a user may be ignorant doesn't mean anyone should try and scam him. You should escrow at least 0.5 if you are going to have 10 participants, and later if you think that the campaign is not worth it, you can state it in the thread, close it and inform the escrow he will provide you with 100% refund(unless he charges a fee for it, which most escrows rarely do these days).