If this was a no-snow area I may be inclined to allow it. The terminal is already 18" above the roof; an additional 12" would put the panels 2-1/2' above the roof.. which would seem like enough space to me.
However, if there was a chance for snow buildup, or the installation of the panels would significantly obstruct air flow, or channel the vent gases to an intake or window.. I may think otherwise.
In the interest of being reaosnable I think I would have to see the entire plan and existing conditions before making a decision.
However, pwood does have a tenable position imho.