I like this idea. I would take it further and say that the commander/observer should get a little rework so that its deeper than the observer just tagging along behind the commander.
What if the commander marked a target and then the observer had to designate it to call in. This would allow the observer some more autonomy (just needs same line of sight on the target) and give that class some more purpose (he wouldn't have to be up the commander's ass all the time), and would also balance out the spam-ability of the fire support.
The commander's order could make the colored smoke pop up, and then the observer could actually call in.
I thought of an idea before. A one-time use AA ability. There are two ways to use it.
Commander activates it, off map AA will activate for 30 seconds. They'll counter any incoming A-10 strikes within the 30 second window.
Spotter paints the helicopter with a laser designator. The Commander activates AA. A missle comes from off map and hits it.