I will agree, at times there has been merit, and leave it at that.

The most important point you make is the need for a single securities regulator. Depending on who you are Canada is either the Wild West or a laughing stock because of the lack of a single, powerful, unifying regulator.

Canada is the only G20 country without a aingle regulator. Quebec and Alberta are the parochial and eternal roadblocks. I say screw them, let them go it alone. 

IIROC gets its orders from the Provincial regulators. Not the Banks. It is funded by a formula requiring Dealers to pay fees based on its size and activities. If there was a single regulator, IIROC and all its activities would be subsumed by the single regulator. 

Banks are overseen by the Superintendent of Financial Institutions. 

ATS's would be better overseen by a single regulator. To abolish them would limit competition and increase costs. But yes, currently they can distort the market.

All or none, or minimum trade blocks would stifle trading and market pricing. Painting the tape is only one of many illegal trading activities better controlled by a single regulator.