If I'm reading you right, you have a few things mixed up.
Trades made on exchanges are generally not made on the blockchain. The only blockchain transactions involved in trading at an exchange are when you send BTC in and withdraw BTC out. All the rest is done on the exchanges internal database and doesn't encumber the Bitcoin system at all.
I don't see how destroying small amounts of BTC would help. Miners can already decline to process transactions without fees.
This were my exact same thoughts when reading this.
The exhange trading has nothing to do with movements on the blockchain. Only withdrawels, deposits and the exchange moving the funds around are processed on the blockchain. The rest is handled on their internal systems. There will be no massive extra transactions because of that.
Destroying a certain amount of coins on each transaction already kind of happens in the form of miners fee. Although the coins don't get destroyed, they go to the miners as a reward. Miners generally don't include transactions which have no fee attached to it, so in theory this should prevent massive spam.
The problem is that people are sending a huge amount of transactions at either no fees to make a huge back log, or they are sending transactions with a fee at a loss to show there is a problem.
