I have long been a supporter of this concept but I have always felt that it's just as easy to evac the injured patient from the hot zone into the loving arms of a EMS Crew that can do just the same amount of skills that the tactical medic does.
There may be some situations where a medic in the thick of things is a great thing, but you should be able to evac that injured person out quickly in many if not all circumstances.
I think it's just like so many other things in EMS and life in general, you want the biggest and best and quickest thing so why not put a medic in the hot zone.