[Help] weapon damage and criticals

Im currently working on the mod project for species diversification and one of the things i really want to do is alter how damage is delt to ships.

weapon damage (this is a big one i hope i can implement, though capital ships may be left on out this):
Autocannon 100% damage to shields then 100% damage to hull (basic damage)
Missile 75% damage to shields 25% damage to hull (basic damage, increased chance of causing fires)
Laser 50% damage to shields 50% damage to hull (basic damage)
Wave 125% damage to shields 50% damage to hull (still on the drawing board)
Phase missiles 75% damage to shields 115% damage to hull (still on the drawing board)
Plasma 125% damage to shields 100% damage to hull (has a burn/melting effect when hitting hull)

This is quoted from my forum post.
Basically i want these weapons to do the said % of damage (out of their total damage) to either hull or shield.
For instance with missiles i want 75% of their damage to hit shields and 25% to hit the hull (even if shields havent been depleted) is this possible? and if so how?

In addition to this you'll notice i want missiles to also have an increased chance to cause fires. How would i got about doing that if at all possible.

If that isnt possible then i would like to know how i could increase the chance of causing fires overall.
Thanks in advance for any help!