That's an interesting idea.

You have what happen to be two very different gameplays here: The bomb and the bounty. Even if they seem two faces of the same coin, they look very different to me. In the "bomb" part there is no motivation to attack and conquer, and this goes somewhat against the main purpose of this game. The "bounty", however, looks quite interesting.
Why don't you concentrate in articulating a good proposal for the bounty option? This is the "hold the flag" type of game, with an added twist because you don't know where is the bounty. This encourages people to attack, to avoid the other player winning just in case he has the bounty. Once you know where is your bounty, you can protect that territory. But also you have to be careful, because if you leave the rest of your empire unprotected, won't have enough armies to protect the bounty.
So my suggestion is: Instead of having two suggestion in one, concentrate with the bounty. This could work.