Would you say the same about Fiona, Evangeline, Adrian, or Rhys being allowed leadership positions?
I would consider Fiona, given her history as a Warden, assuming that she respects the chain of command of the Inquisitor, and could bring a plethora of mages under the banner of the Inquisition.
And I think Cass is gonna have a leadership position regardless of you liking it or not, to be honest.
I certainly hope I'm not railroaded into that being the case; I prefer having agency during my comrades, and the lieutenants of the organization that's supposed to be shaped by the player.
Honestly, I thought Dragon Age II making most of the companions mandatory was a mistake. For a pro-templar run, having to accept apostates is a hard line of thought to process; I'd prefer to avoid those kind of complications in Inquisition, where I'm forced to accept companions because the Plot Dictates.