I'm sorry, but I think you're pretty confused so your assessment is almost completely off base. It seems the one legitimate point you have is that exchanges prefer a %-based fee whereas on OpenLedger they would get 80% of a flat network fee (at least in cases where the exchange is the registrar and referrer). I would agree that's a problem and I hope it will change in the near future.
Consider the biggest external exchange, okcoin. Currently, they collect fees in CNY and BTC. If they came to bitshares, and opened a BTS/OKCOIN.CNY market using their OKCOIN.CNY IOU token, the would only collect fees in OKCOIN.CNY, not BTS.
I suppose they could create OKCOIN.BTS, but that's kind messy.