The idea you suggest already exits for stocks in the US with very high prices because the minimum increment doesn't scale with stock price. For example, Google is $700 a share, making the minimum $0.01 price tick equivalent to 0.0014% vs. 0.08% for a $15 stock like Bank of America. HFTs generally don't even bother with stocks like Google because they aren't profitable enough. The rebate and value of making a tick goes down as price increases. This causes spreads to widen and these stocks are generally harder to trade for the buy-side. Not a good situation.