To consider sidechains and think only of the good ideas it enables and ignore the perils is stupid
I don't know where to begin. you can begin comprehensive reading at page
698 
but we've left you guys dozens of page to come up with a plausible, considerable risk that would warrant not to integrate sidechains to Bitcoin and you have continuously failed.
face it, the upside is considerably more interesting AND plausible than any of the strech of the mind paranoiac scenario your team has come up with