proposed Optional Rule's optional Rule: Weapon Trait - Burrowing
Burrowing only modifies damage to armor.
For 'Ablative' armor: the weapon with Burrowing does 2 damage to armor for each actual damage point done to the leftmost armor section. Any single armor box left, is destroyed by 1 point of damage (the extra damage is not transferable). Damage to the other Armor section by burrowing weapons is - do 3 damage, get the 4th box of armor destroyed as well (if the vessel has that many) so 9 points of armor in the 2nd section would only take 7 points of burrowing weapon damage to take out that armor section and 9 points of armor in the 1st section would only take 5 points of burrowing weapon damage to destroy all the armor in that section.
For 'Incremental' armor: the weapon with Burrowing does an extra point of Armor damage for each 2 regular points of damage done on the leftmost armor section, and does an extra point of armor damage for each 4 regular points of damage done to the center armor section.
Example of weapon trait in use vs Ablative armor: The Methosians love their armor and have chosen to use ablative armor. Their Battlecruiser in standard has armor of 7L - 7C - 6R, which translated to 7 - 6 - H1 - H2 - H3 for our Ablative vessel. 3 Gweenee vessels: a Frigate and 2 Destroyers (new builds with Burrowing) find the BC alone and without escort. Battle ensues. In a stroke of luck, the BC long range weapons are ineffective while closing, the next round sees the two forces close, The Gweennee have initiative and DD#1 fires his 2 Burrowing weapons at the BC doing 2 points of damage , this takes 4 armor off the leftmost section of armor. The Methosian BC's main weapon again misses, but it's secondary weapons both hit DD#2, getting 1 box from taking down it's centre hull structure (nothing left of it's leftmost armor/hull and taking the center armor out as well.
It fires back but misses. Then The Frigate with a standard weapon attacks the Methosian BC and does 2 damage at this range, that leaves 1 box of armor left in the leftmost compartment. The next round Has the Gweenee DD#2 attack first, doing 4 points of damage. The 1st point of damage takes the last armor of the leftmost section, no carry over of burrowing to the next section with that 1st damage point. The next armor is hit by 3 points of damage from a burrowing weapon so the other section loses a 4th point, leaving it with 2 points left. The BC fires on the injured DD#2 and destroyes it., DD#1 isn't in his weapon arc save for some close in weapons that are out of range, so he fires on the Frigate with his secondaries, and nearly takes it out. The Gweenee DD#1 fires his Burrowing battery and also does 4 points of damage, if there had been 5 points of armor left, the Gweenee would have gotten a free armor hit, but because there were less, (2) it does standard damage from now on as after the first 2 points of damage, only hull is left. which it does 3 points to, which is not enough to get thru to the middle Hull. The Gweenee were able injury the BC before they met their demise, but it was more main battery poor shooting by the Methosian. Hopefully the Gweenee Cruiser with Burrowing will fare better vs their enemy.
Cost multiplier - T.B.D.