imo exchanges are looking to merge partly for synergies, but also to position themselves for the legislative drive for vanilla OTC contracts to move onto regulated venues. They're not doing it because of glass-steagall the sequel.
HFT might well be hit by regulation too, whoever the...
Moving stops to break even mechanically (like after XX% risk or whatever) doesn't make any sense, just like treating every trade as the same R:R doesn't really make any sense.