The damage deck could just be doubled. Sell it at any flgs during tournaments. Unless you want to play tournamanet games it wouldn't be necessary. Keep the same number of double damage cards. Add other things like-
Core breach - When this ship receives full damage the ship explodes, dealing 1 crit to all ships at range 1.
Energy overload - all upgrades are turned down, action: roll one attack die + 1 for each crew member. On a hit you turn over an upgrade.