Item Decay Source 3 (Source)
While many of your ideas are sound. This entire section is just backwards.
Armor works the exact opposite of how you say it does. Condition decreases based upon the mount of damage that gets through it, not the amount of damage that it prevents.
Thus, a 43% Stun resist shield, when hit by a Geo Pistol for 800 points, gives the following benefit:
800 * 0.25 (75% PvP Resist) = 200 200 * 0.50 (AP0 vs. AR1) = 100 100 * 0.57 (43% Resist removed) = 57
PSG degrades by 57 points, and 57 points goes along to hit your (hopefully stun-layered) armor.
If you use your Mk1 PSG at 7% Stun resist, you get:
800 * 0.25 (75% PvP Resist) = 200 200 * 0.50 (AP0 vs. AR1) = 100 100 * 0.93 (7% Resist Removed) = 93
PSG degrades by 93 poitns (36 more than with the other) and 93 points goes along to your armor.
That's an increase of about 63% more condition decay and damage.
Now, on to the condition. "Most PSGs" do NOT have 3k condition. The new "Imperial Prototype PSGs" do, but Mk.3s tend to have about 1k, for instance.
Oh, and one more thing. Be careful on low-resist armor/PSGs. If a T21 tags you for say just 800 damage, against your 20% Energy Resist PSG, here's how the calculations work out:
800 * 0.25 (75% PvP Resist) = 200 200 * 1.25 (AP2+ vs. AR1) = 250 250 * 1.25 (AP3 vs. AR1) = 312.5 312.5 * 0.80 (20% Resist Removed) = 250
Yup, that's right. The T21 actually did more damage by hitting you with a shield generator on, than without. You'd need a 36% Resist to Energy at AR1 just to even out against the AP3 of the T21. You'd need that 20% just to even out against an AP2 weapon.