So the skyshields are to provide 4++ and put your relatively weak armored Boomguns. With a 1 in 6 chance of don't press that (meaning 1 will roll it every turn) and the fact you will pack 3 on each platform seems a bit chancey. 4 SAG also is frought with peril as you begin to look at the laws of averages on the rolls (IMO).
I think gimicky for sure. It could end well or extremely badly for you. However, your opponent needs to focus on the guns (well...the guns that don't take themselves out) while your boys get across the board to deliver some love Ork style.
What will the Guns be doing once the boys get on the other side of the board (big risk of scatter). Can the Skyshield be destroyed? What happens to models deployed on it? How many HP on the looted wagons?