Why? Why should it appear to be a dragon?
Good god, this is a fantasy game dude! don't trip. If he wants a dragon shaped conjuration spouting fire, then so be it. I think that'd be awesome too, the ideas he's mentioning.
But you can't dominate conjured creatures. Combos? Burden 100 pounds, back off, pelt with fireballs. Not as advanced as a power attack, but it works.
You may, depending on what you're conjuring and from where it is being conjured. You can't control the summoned lesser daedra in TESIV because they were servants from Oblivion, under the control of the daedric princes. But you could summon a creature from some other place on Nirn and possibly have control over it, although that hasn't been discussed or implemented in the video game series yet.