- Click image to enlarge.

I'm not experienced with the coding, so I would need help with that. Two things before I get into the rules:
1. The image is in the public domain in the U.S. so there isn't a copyright issue.
2. The colors will be toned down, the bright colors are just to make illustration easier.
Now, the rules would be as follow:
"Territories": 15
"Continents": 7
Continent Army worth by color:
Purple: 6
Yellow and Blue: 3
Pink, Orange, Green, Red: 2
Attacks:
All Yellow, Pink, Orange, Green, Red, and Blue can attack each other.
All Yellow, Pink, Orange, Green, Red, and Blue can bombard Purple (Caesar).
Purple can attack within itself, and Purple's (Caesar's) chest can attack Blue's (Brutus') chest.
In other words, if Caesar can stay alive, he can attack through Brutus, but if the conspirators succeed in "bombarding" all of Caesar, there's no way to conquer any of him (he's dead). Then the conspirators have to fight it out amongst each other. The incentive will be to get rid of Caesar, but players who start as conspirators may not want to weaken themselves by taking care of Caesar, therefore making them susceptible to attack from conspirators who chose to consolidate their power as opposed to bombarding Caesar. In some games this could give Caesar a chance to survive "win over" Brutus, and take the win. If the proper balance isn't created, Caesar could either always be abandoned or instantly bombarded to death. (I might have to drop the value of owning Caesar in order to create less incentive to wipe him out immediately. We'll see.