Well, recently, i wanted a dragon with a more... varied... breath weapon. so, i made a size 4 "gun", however, in the same way the common minifig's 1d6 armor becomes 4, the size of the weapon became 1d6... do it does (1d6)d6 damage. we do not roll for size each time or for the beginning of the battle, but we roll an extra 1d6 for each of the stat's in the "gun" each time it fires.
basically, VARIABLE WEAPONS: (1dX)dY damage:
a variable weapon may be declared in set up, and the value 3, 4, 6, or 7 in the size may be replaced by a 1d4, 1d6, 1d10, or 1d12, respectively. the weapon is treated as the highest value possible for size towards the size limit of weapons on a creature or vehicle, but as the equivalent (1d6-->4) size towards cost in CP.
roll a 1dX (1d4,1d6,1d10,1d12, ect.) to determine a value of R. roll a dice of size Y for each value of R. an original roll of 1 is a total critical failure, and no more dice are rolled unless the host allows it or the player's agree. any other 1's are removed, and all critical successes with an individual die count towards another die.
(1d6)d6 damage (equivalent 4d6)
Player 1 rolls a 4 for his damage roll on a variable size gun. he then rolls a 3, 1, 6, and 4 based on this. he removes the 1 as a critical failure, and rolls a 2 for the 6's critical success. the total damage for this roll is 15.
(1d4)d10 armor (equivalent 3d10)
to block player 1's damage 15, player 2's tank has a variable armor "force field", with a "size" of 1d4 effective structure level 3. he rolls a 1. Critical failure! player 1 decides to have pity on player 2, though, and let's him continue rolling. so he rolls a 6. counting as a critical success, he rolls a 2, for a total of 8. he still loses, but the over kill to the next unit in line is significantly reduced.