So I noodled out a nice little mechanic for figuring out how a Titan's systems, the battlefield conditions, and the players factor into the cost of successful actions: Adjusted Cost.
The base cost of any action would be determined by the cards played off the Strategy deck, so a Titan engaging in an Attack-type action against another Titan engaging in an Attack-type action might have a base cost of 2 Strategy cards for the price of success.
In the case of Move-type actions, the base cost is adjusted by traction: Where the traction of battlefield conditions is greater than its Propulsion-system's traction, the difference is the number of Strategy cards to be burned in offerings to the gods (spent for success).
In the case of Command-type actions, the base cost is adjusted by battlefield conditions again.
In the case of Defense-type actions, the base cost may be adjusted by battlefield conditions and the option to overload Shield systems. Overloading, naturally, will incur Light Damage to the system.
Finally, in the case of Attack-type actions, the base cost will be adjusted by several factors including battlefield conditions.
At first I wanted to allow players to spend extra cards to increase the Power of shots, or to increase their accuracy somehow, or to defend against that, but I realized that it boils down to players dumping cards to make otherwise successful actions unsuccessful, or pointless.
The Attack-type actions are also dependent: A Titan needs to successfully execute an Arm Weapon action and an Acquire Target action before they can successfully execute a Fire Weapon action. Three opportunities for failure where an opponent is trying to make life difficult by changing the base cost, and shooting back.
An unsuccessful Fire Weapon action runs the risk of wasting ammunition. Failing to Arm Weapon or Acquire Target means that the other player might get the first shot. It would simplify things to simply allow a player to choose the affected system, provided it is available. After all, that is why all systems have orientations, so that they can defend themselves via orientation, as well as position, and action.
Simply put, I'm inclined to simplify the Fire Weapon action so that Gatling Blasters can be used to strip shields, and Volcano Cannons used to execute Titans. That they might miss, might fail to cause sufficient damage, or whatnot, will be accounted for by I think that the combinatorics of the game can be minimized thanks to the uncertainty created by the turn sequence. Players should be rewarded for gaming the system in a game, I think, rather than being punished, or the behaviour being politely ignored by the rules - the point of rules is to direct that habit towards constructive and enjoyable use.
Although I've also been debating whether to have players draw directly off their decks to the card played that round, or have them play out of a hand of cards that can be replenished from the Strategy deck. I'm inclined for the hand to prevent the issue of unchecked bidding where the initiative is concerned. I should also like conditions where, given the conditions present, an otherwise simple shot will fail. The trick, I think, will be making sure that the costs adjusting the base cost are a distinctly short list of +1 card so that players get to make a choice between the cards held in hand, rather than paying out against quickly opaque Strategy decks (and not falling prey to the problem of drawing otherwise useful actions that must either be passed or failed when they are not useful!
Rather than complicating the adjusted cost with arcane algebra, I think it's best to think of the results as benefits until I've managed to suss out the live options and dominant strategies entailed by a much simpler system. In the meantime, limiting players to playing a hand should make it easier to incorporate the more complex version should the simpler limit game-play.