If we're doin' conquest, we gotta do this right. 

We'd need a legitimate political face and stance for the populace to eat up, but one that quietly puts the lion's share of the power in our hands. The ideal result would be that we take power without drawing the ire of the U.N. while putting public opinion between honest heroes and us. 

Since a bloodless victory is unlikely and boring, I'd also recommend a cell-based black-ops division. They would be handling the assassinations, blackmail, and raids on targets of opportunity that our agenda will require while minimizing the possibility of leaks.

The most important thing is to leave our legitimate face an out to 'condemn' such 'villainy' and maintain his political clout until we can assume direct control, perhaps some imaginary terrorist organization. As this organization's rep builds, we would also gain a voice in the underworld without them knowing who they're truly dealing with, further extending our influence without exposing our core membership to scrutiny.