One of my favorite things about diplomacy is that it is a challenge to battle. Unlike competitive games, it has wars going all over the place, with many different players and it's a simulation of real life. Giving troops to your allies already is possible (Gift them X Armies on a territory, then take it back). You don't need a card for everything, the diplomacy card is already overpowered:
https://www.warlight.net/Forum/93805-discussion-permadiplo
Edited 6/7/2015 12:20:51