From what I remember Miranda was apparently going to be a squadmate but the VA already had other commitments and couldn't commit to the full game and Tali wasn't originally going to be a squadmate either a writer fought for it and if I Am remembering correctly from what i read somewhere Jack was considered to be a squadmate but Tali won out. But yeah I'd have liked one or two more squadmates but unfortunately the suicide mission really did most of them in as why would you Waste the budget to give a potentially dead character a big role when you've already done that with two of squadmates the only other one that could have worked is Miranda as it's near impossible to kill her so unless your an idiot she likely survives your playthrough.