A useful concept here (which I picked up from a pro player of Magic: The Gathering, but exists in many other environments) is "board state." A lot of the research I've seen in game theory deals with very simple games, only a handful of decision-points followed by a payout. How much research has there been about games where there are variables (like capital investments, or troop positions, or land which can be sown with different plants or left fallow), which can be manipulated by the players and whose values affect the relative payoffs of different strategies?

Altruism can be more than just directly aiding someone you personally like; there's also manipulating the environment to favor your preferred strategy in the long term, which costs you resources in the short term but benefits everyone who uses the same strategy as you, including your natural allies.