Diplomacy's primary ability can seem weak compared to the others. I have a couple ideas for spicing it up.
Idea 1) Alter the Primary Ability by adding one of the following.
A - Choose a player, that player must give you a promissory note. B - Spend X influence to make a player give you a promissory note. Any players may spend a combined X influence to negate this effect.
Idea 2) Alter the Secondary Ability slightly. So it reads as follows.
C) Give the active player a promissory note to ready up to 2 exhausted planets. D) Spend 1 command token from your strategy pool to ready up to 2 exhausted planets. The active player gains 1 command token for each token spent in this way.
What do you think? Which changes or combination of changes would be best for your game?