Great ideas.. I like it. You state that Tank armor should provide the best AC bonus.. hands down. Everyone here knows that's the way it should be.
You also mentioned Backpacks with 'worthwile' modifiers.. well they are comming in the next patch (13.60) and include such packs as
Black Button: +5 to all Spying skills.
Cold Front: +280 Cold AC
Mountain Top: +10 NanoC. Init +20 Max Nano
Sniper: +10 Ranged Init +2 RangeInc. Weapons
Now granted these aren't DRAMATIC increases.. but they are nice. They require 200 in Adventuring.. (another reason to raise the skill) and don't cost an arm and a leg at the level you can start using them (30+).