Diplomatic Rules for 1940 A&A:GW Start?

Hi, all. First post, found this place looking for big A&A maps, and was brought here by the Global War thread (found the map via Google, followed the trail, and voila, forum!) The reason I was looking for map ideas is that I’m working on putting together a 1940-Start Point game. The project itself is going to have a few different things involved, but the current “hard part” is working out some rules for deviations from historical alliances and such. I’ve got some ideas, but would love to hear about anything the more experienced forum veterans have seen.

Brief description of the “game state”:
-I’m using a slightly tweaked version of the map from the Global War thread
-The world is set to mimic early 1940, right before Germany enters France.
-France, Italy, and China are playable nations (though China naturally has very few resources available)
-Germany begins at war with allied Britain and France; Japan is at war with China.

From this point, I’d like the game to be able to go in any direction the players of the day feel like going. This could include “real history” (Italy joins Germany quickly, Japan eventually brings the US in), but I’d also like for things to turn out differently (a smart Germany never attacks Russia, for instance). Here’s what I’ve got in mind so far, please provide suggestions or ideas from your own experiences.

**-**Countries must pay to declare war on a nation. This represents army mobilization, expending political capital, stuff like that. The cost to declare war on a given nation varies depending on the real-world situation: Italy would spend next to nothing to declare war against France, but would have to pay a metric crapton to declare war on Germany. Naturally, being attacked results in a free declaration against the aggressor.
**-**Likewise, entering into an alliance requires the expenditure of capital, and countries that historically allied will find it easier to do so. The specific rules on what determines an Alliance vs. just fighting against the same enemies will be determined later (allies will be able to pass through each others’ territory, for instance, and will share victory conditions). Nations will be allowed to give a certain amount of $ to other players to help entice them to join the fight; this might be the major motivator that brings a US or USSR player into the war.
**-**Declaring war on a nation that has allies will result in your becoming at war against those nations as well (I’ll have to decide if a player will have to pay for the Declaration against every nation they’d end up at war with, or if this’ll be a method for a “cheap declaration”. I’ll probably go with the latter.) I don’t expect to include rules for breaking alliances beyond surrender.
**-**Attacking a neutral costs capital as well, but is generally a much lower cost.
**-**The cost for the United States to enter the war begins extremely high (they may even be unable to enter the war initially), but this cost will decrease over time, possibly with a simple turn-based “timer”. As the war goes on, the US starts gaining the ability to deploy more troops, and their cost to declare war against Germany or Japan goes down. This sort of timer would also encourage Japan to attack the US first, before their power level gets up (or before Britain just pays for the US to enter the war).
-The US will be heavily limited in what they can deploy before actually entering the war. Similarly, they will gain no income from their Convoy spaces until a certain turn is met (or upon entering the war).
**-**I do know that I’ll have to work something out regarding the USSR. They’re in a similar situation to the US as of this point in time (not actually involved in a shooting war with anyone); I may just let them be, and leave it up to the players as to how to proceed.

One of the difficulties I know I’ll have to address is having two nations not currently at war, and finding a way to ensure that they do eventually enter the fight somewhere. It could be hard to motivate a USSR player to do anything other than just build up, though having limits on non-war troop buildups are likely.

At any rate, thanks in advance for your advice. :) I’m looking forward to seeing what other folks have tried in the past.

EDIT: Came up with a much simpler idea for the US “declaration costs”.