I think it would be really cool to call in some artillery. Im not sure how it would be handled, if players would control the arty or if the AI would and you would have to call it in, We could have naval bombardment also where you could call in the big guns.
1.) If players control arty I guess they could have other players be forward observers and direct the arty
2.) Would be fun to set up on a hill and blast that AF in the valley a few miles out
3.) Conversley imagine the fun takeing out an arty position, you call in the fighters to take it out
4.) Smoke missions, obscure you movement for you
5.) Hehe have that arty pre planed to be droped on your position when your being overrun (saw that in a movie, forget which

)
6.) We basically need 1 arty piece to start off with and we can build up the sytem from there on how to handle it, how to call it in, prioritize fire...