How about a pt= selectable payout parameter in the "userpass" config of miners then you could still have peace of mind, still have minimum and maximum limits. Let the user have the responsibility to decide what is a reasonable risk of loss, after all pool mining and trading is risky anywhere.
So if I mine to your address with pt=500 for a little bit right around payout time what happens then?
setting your payout threshold that high would be idiotic LOL Letting that much sit on pool would be more than I would risk the loss of. Again poolwaffle would have to decide what min and max threshold are limited to