I see no reason why the bitcoin GUI shouldn't allow to send low priority transanctions when sending small amounts. It could just add a warning: "if you do not pay a fee, your transaction may take a long time to be processed (a day?)". Also (but I think this has been suggested already), it should be possible to pay "milliBTC" fees. Paying a 0.01BTC fee when you are sending 0.05BTC is just not acceptable.