Okay, figured out the things for making your own weapons.
+2 damage = +1 CP and +0.5 Use
+3" range = +1 CP and +0.33 Use
Two-handed = Round CP and Use down instead of up
They work backwards, too. They don't well with launcher types though. Also, they can be used to add to a minifig or creation under a circumstance and with a choice of whether they want to be used or not. Also, decrease the cost by 1CP such as:
+1CP = Increase damage of close combat weapons by 1d6, but increase the use rating by 1 if you do so
Some more houserules:
5. As seen in the above stat-changers, the allowance of 0.25, 0.5, and 0.75 CP is allowed, but must be rounded accordingly.
6. A pilot is considered to use his Movement Action towards piloting whatever he is driving and his regular Action towards operating any other controls.
7. Explosives fired from a launcher can have unlimited ammunition, but you must pay triple the price and the launcher must wait one turn between shots.
And I think this last group may be it. They are special additions that you can give to creations and minifigs for a price.
+2CP = Natural body armor. Same as regular body armor, but no move penalty
+(0.5 of Base CP without weapons) = If hit by an attack, flip a coin. On tails, the defender takes no damage.