Mayhem, we too play with NAs. Actually we did two games in a row with all NAs. On the first game, Germany bought 1 AC and 3 subs on G1. That left him with very little ground force but he just held his cocoon and on G2 built just INF and ART to compensate. In the end, Axis won the game and the subs made the Allies loose at least 60 IPC through the course of the game (which wasn’t very long, maybe 7 turns). Plus the allies were always threatened by a mighty fleet of 1 AC, 1 DD, 5 subs (attacking on 3s), and 2 trannies (one of which was built later on) plus all german air force.
In our second game, Germany made a G1 purchase of 1 AC and 8 INF. Every turn thereafter Germany purchased 1-2 subs. The end results was the same, an Axis victory, but it was a lot safer against Russia with the additionnal 8 INF on G1.
No matter if you play with NA or not, a G1 buy of an AC is HIGHLY recommended.