It will work. The majority of HFT's illicit profits accrue from speed arbitrage *between* the exchanges, not from a speed advantage at any particular exchange. A co-located HFT server at an exchange sees an order, and, in anticipation of that order representing a larger order that can't be filled in full at that same inside "best" price at that exchange, trades ahead of the order by sending a buy/sell order to other exchanges faster than the original buyer/seller can, resulting in a riskless vig for the HFT trader.
By delaying orders on all exchanges by 500ms, the benefit of early-access to incoming orders on any particular exchange is eliminated because all the exchanges will have 500ms of order price discovery incorporated into their SIP, the consolidated price representing the aggregate of the best prices for all the exchanges.