Deck of cards, one for each neutral.
Start of each player turn, top card is drawn and disposition of country is determined.
Each neutral will have a scaled historical bias based on likelihood of joining each side, expressed as a number in favour of either side.
Each side places a secret bid in IPCs from their banks to influence the result, winner gets control. Money bid by both sides is considered spent. Ties are replaced in bottom of the deck.
Result could also be influenced by other factors, for example presence of units in a bordering tt.
Cards can be placed in “historical” order by number based on when they were first engaged, or shuffled for random events.
Card drawn for neutral already attacked is ignored.
OR
Cards are dealt randomly to the players (half for each side for balance or same for each power?). Maybe 5 cards per side with a draw deck. Start of every player turn, that player can play a card from hand for each side to bid upon.