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.