Really clever and well thought out design. I love the way you've tuned the player decision space to just the initiative area, with everything else randomised. Mathematically it comes down to a blackjack like (but with way more depth) risk calculation setup.
My only thought is around length. Because the lines can move forward or back, and the player can repair planes, the game has the potential to go on for a while. Like a real war I suppose. When playing the later, harder missions, I generally ended up going backwards, and got stuck in the middle for a while.
Mind you I'm getting very bad dice... 4 ground and 2 planes be like welp :p