I'm thinking for the boss I might "borrow"(sounds better than steal) the concept of "bits" from Gundam. The boss will be able to break off multiple gun pieces which will be able to function on their own. While the other bosses have been big and slow, this boss will be smaller and faster.
Also, I fixed a big problem with the dropping of items. Before, the little transport ships would sometimes drop an item the player already had, which of course, made the item worthless. Now, instead of dropping a duplicate item, the transports will drop the bomb power-up. This also means that the player will only get the bomb once they've gotten one of the good power-ups.
Finally, one more thing I've been thinking about is adding more weapon pick-ups with limited ammo, such as beam cannons and homing missiles. Unlike the main gun, these would only have a set amount of shots. I'm thinking they might only be dropped by certain enemies as well, so for example, the player could only get homing missiles from an enemy that uses homing missiles. I would, however, throw in a super beam cannon power-up that would be rare but that could be dropped by any enemy. Meh, I'll think about it, because I think it would be a fun addition to the game.