Another variation for US IPC calc would be 3Tn + 2d6 (ie. 3 times turn # + 2d6), this gives US more incentive to delay entering the war. For turn 4, the calc ends up being the same as 8+2Tn+2d6 rule.
Also, on your point about capital ships - we use a 2 turn build rule. Where on TURN X you can put down anything from 1/2 to full price, with balance due on TURN Y you put into action (which doesn’t need to be the next turn). Exception: You can purchase and deploy capital ships on TURN 1.
