Seeking input on co-op combat system

I've been kicking around an idea for a cooperative game for a couple of months, and I wanted to get some feedback on my idea for a combat system. Fair warning, this will be a long post, but I think the system itself is much harder to write about than it would be to demonstrate with physical components or pictures.

The concept of the game is that each of up to 5 players is a crew member on a starship (for less than 5, some players will play more than one role).

Each crew member starts with 3 custom d6's, although later upgrades or damage to the ship may result in rolling anywhere between 1 and 5 dice. I've attached an image of the dice below, with reach row representing the faces of a single die. At the start of combat, each player rolls all their dice, then take turns "spending" dice in accordance with their role. After all players take a turn, the enemy ships then have a chance to take action. Only spent dice are rerolled at the start of the next turn.

Each of the dice has a star symbol which is used for special abilities, which are different for each role. Each die also has a pass icon (the cube with an arrow), which can be spent along with another die to loan the second die to another player, allowing him to use it as if he rolled it this turn. Here is a description of the roles:

Gunners (2 Players)
These players focus on attacking enemy ships directly, and they care about the symbols on each of their dice. Diamonds, Triangles and Hexagons each represent different types of attacks, and each gunner selects one type of attack to use on his or her turn, spending all dice with the matching symbol. Enemy ships may have one or more shields, with each shield having one of three colors (blue, green or red), each of which corresponds to a symbol (diamonds, triangles and hexagons, respectively). Spending dice of the matching symbol destroys one shield per die, while non-matching dice destroy 1/2 of a shield each, rounded down. Thus, attacking 4 red shields with 3 hexagon dice would destroy 3 shields, but 3 diamond dice would only destroy 1. The X represents a miss, and the player may choose to spend all his X's in order to reroll those dice on his next turn. Stars are wild and can be spent with any set, but only to attack shields of the matching color (i.e. if a player could spend a star when spending diamonds to attack blue shields, but not red ones). Once an enemy ship's shields are down, gunners may directly attach the ship's hull, with each die spent counting as one hit, regardless of symbol. Stars may not be spent to attack a ship's hull. When the ship runs out of hull points, it is destroyed.

Fighter Commander (1 Player)
This player controls the ship's wing of starfighters, which begin by engaging opposing fighters, but are able to attack enemy ships directly after enemy fighters have been destroyed. This player cares about the numbers printed on his or her dice. The player may spend as many dice as desired, as long as those dice are in numerical sequence. Thus, if a player rolls 4 dice and gets 1, 2, 3, 5, he could spend the first three dice or just the last one. Each dice spent destroys an enemy fighter, or counts as 1/2 of a hit on a capital ship (shields or hull). For each star this player rolls, he may ignore the number on that die, and instead spend it to add a multiplier to his total number of dice spent. Thus, the best possible roll on 5 dice would be a sequence of 3 numbers, along with 2 stars, for a total of 9 hits (3 x 3).

Engineer (1 Player)
This player helps ensure the ship maintains power and has access to a range of special abilities to help complete the mission, based on the upgrades installed on the ship. The Engineer tries to complete chains of dice based on the background and foreground colors of her dice. Dice may be chained if the background color of the die matches the foreground of another die, or vice versa. Using the convention xY, where x is the foreground color and Y is the background color, an engineer might spend a chain three dice like this: rB -> bG -> gB. The longer the chain an engineer can produce, the more energy is stored in the ship's battery bank. I'm still finalizing the relationship between chain length and energy, but I'm leaning towards 2-3-5-8-13 or something similar. Systems on the ship, such as repair bots, tractor beams and thrusters, require various combinations of energy and Star dice rolled by the Engineer to be activated.

Ship Captain (1 Player)
The captain is responsible for protecting the ship, and is tasked with managing the shield generator. The captain tries to collect sets of matching background colors. The captain may choose one color each turn, and spend all the dice of that background color to provide shields for the ship. Each die spent prevents one hit that the ship would take during that turn. Each hit that is not absorbed by the shields damages one of the parts of the ship (determined by rolling another custom die), and that crew member loses one of his or her dice until the ship can be repaired by the Engineer, or reaches safety. Star dice don't have any effect for the captain, but he may freely loan any or all of his dice to any player, without having to spend Pass icons to do so. Additionally, in between missions, the captain is the final decision maker regarding which upgrades to purchase, and which missions to undertake.

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My hope is that the various roles will appeal to a variety of play styles, and that the use of Pass symbols will encourage cooperative play in order to maximize the effectiveness of the whole team, especially since players values dice using different metrics. I've run the probabilities on each of these systems, and I'm pretty happy with the results. (I'm happy to post my findings if anyone is interested).

So, after all that description, what do you think? Does this seem confusing? Any points that could stand clarification? Which roles excite you and which seem boring? Thanks as always for the input!