After much work, thoughts, comments etc:
no bolt on rules - armor and shields are represented by traits. You want them, you take them, you do not want them, fine.
we have ONE level of armor, we will call it Heavily Armored. Lower levels of armor are assumed to be reflected by the figure's C score.
A Heavily Armored figure adds +1 to his C roll after the roll, when losing a combat. If this changes his being doubled, tripled, etc, it means that the armor has stopped the blow. In no case the result will be better than a tie.
Magic,the Penetrating trait or the Crossbow trait ignore the Armor effect.
Shields may be abstracted or reflected by the following traits:
Melee Block - blocks melee attacks only
Block: blocks melee and ranged
Expert Block: blocks melee and ranged on a roll of 4+
Magic Block: like Expert block but works against spells as well.
Blocking works like this: if the model has been put out of action, knocked down or recoiled, he rolls a die, on a 5 or 6 (or on a 6 only if the model is surrounded by 3+ foes and/or knocked down), the model may downgrade a OOA into a Knockdown or a Knockdown into a Recoil or a Recoil into a No effect.
If a model has both Heavy Armored and Block, the block roll is performed AFTER taking into account the armor bonus.
There is no limit to the number of blocks that can be attempted in a turn.
both armor and shields are written as generic rules so they may be applied to represent a dragon's scales or the like. DO NOT FEEL FORCED to use them on any character who has a shield or wears a suit or armor. Use them only when it feels appropriate for the figure.
Also, no limitation of movement. If you want to simulate that, just buy Short Move or Slow for the figure, and that will offset the cost of the Armor/Block rules.
It works well, it's unobtrusive, and does not change the game too much.
Also take into account that some fungus figures will have Squishy. Also good for jellies, gelatinous cubes, oozes etc.