Wouldn't that cause the actual wallet balance to be confusing to the individual transacting as his % would change by a different amount then he transacted with. Seems like it could be a source of confusion.
Last I heard was that balance was to be displayed as (yourRealBalance/totalRealSupply)*4,000,000,000. I believe the number of zeros on the final multiplier is still flexible. That part is purely cosmetic, but people do love large numbers.https://bitsharestalk.org/index.php?topic=3024.0
Since you'll enter transactions in the same units in which your balance is displayed, the numbers should all be intuitive. So in this case with a real balance of 30, and a total supply of 4,000,000, your displayed balance would be (30/4,000,000)*4,000,000,000=30,000. If you enter to send 5000 of that displayed balance, it would send a real balance of (5000*4,000,000)/4,000,000,000=5. This would leave your real balance at 25, which would display as (25/4,000,000)*4,000,000,000=25,000 as expected. If you mean people being confused by the transaction fees, I don't think it will be any more confusing than Bitcoin transaction fee deductions.