This is kind of wandering into a pet peeve of mine: turning a process into a "branch". The idea of ISTAR units is a similarly ill conceived notion in my book: ISTAR is a process, and refocusing the work and work spaces of a tactical HQ to integrate multiple source and sensor inputs can probably produce the desired results without creating the need for entirely new sections of modular and carrefour tentage and personnel attached to the HQ.
If I am to get the best results from a TUAV in my role as an Infantry section commander, I would be best off packing a device that a soldier can carry and launch by himself, and which feeds "real time" data to me so I can "look around the corner". In the "Infantry of the Future" thread there is a picture of an Israeli soldier wearing a sort of wrist band TV monitor to do just that. Similar devices can be mounted on vehicles and helicopters (a helicopter gunship with a UAV flying ahead like the Kiowa Warrior scout helicopters do for American AH-64s), expanding local situational awareness.
"Bigger and better" UAVs for tactical headquarters would of course have greater performance and carry more sensors, and a tactical headquarters should also have the means to interrogate "my" TUAV, without interrupting my little show. Each step up the line, there will be dedicated devices, and the means to interrogate lower level devices without interrupting the user. This also cuts through the clutter of who uses UAVs for what: Gunners can search for targets, recce soldiers can develop information for the rest of the team, EW types can read SIGINT and deliver headaches to opposition systems etc.
In a fully developed "Bottom up" system, theoretically there is no need for dedicated TUAVs at any HQ level, they simply interrogate subordinate systems to find out what is going on. Realisticly, the commander needs his own independent means of information (read Martin Van Crevald's "Command in War", especially his thoughts on the commander's "Directed Telescope" techniques through the ages), so HQ level flights are appropriate.
<rant off>