I think you should keep sea invasion to 2 sea zones, as it is very difficult to logistically support it from that far, plus will eliminate unhistorical situations. You should still keep the 8 zone strategical move on the regular phase, but these units dont get to move in the mech phase, with the proposed rule, transports only get to move 15 instead of 16 zones, that can create some problems for the Allies reinforcing North Africa, especially when India and Australia is out of the game.