Stealth in SG2 - how to implement it?

What is stealth from DS2? I assume it is a combination of electronic/EM
countermeasures, thermal ducting and countermeasures, and visual
countermeasures. What is the effect? In DS2, it makes the vehicle harder
to
hit by reducing its effective signature. 

How to best represent this in SG2? 

Ideas:

1) A reduction of size class as a target
2) An increase of effective ECM by 1 or more levels (an open shift that
moves from the defenders ECM die to the attackers guidance or FC/FP die)
3) A stealth die - a 1 level stealth is D4, 2 level is D6, etc. 

Each has advantages and disadvantages. 

1) Pros: Easy to do, somewhat similar in mechanic to DS2
   Cons: Works not a whit against GMS or infantry small arms - useless 
   to size class 1 vehicles. 
2) Pros: Easy to do. Works against all attacking weapons systems.
Similar 
   shift can be applied to spotting rolls. 
   Cons: Means shifting more than 1 die conceivably. 
3) Pros: Extra die is probably most advantageous option for defender. 
   Also works for spotting. 
   Cons: Means attacker would have to beat both stealth and range or ECM
dice. 

I implemented PDS for vehicles using method 3 (an extra die). I'm not
sure
which makes the most sense. 

Q: Can infantry have stealth?
A: Perhaps? 1 level = phototrophic cammie jammies. 2 level =
predator-like
cloak shields. 

Q: Can other vehicles types have implicit stealth?
A: I think perhaps some things like motorbikes have something like this
versus being hit (spot normally - a bike makes noise). 

Comments, rebuttals, other theories, like it, lump it, want to put a
bullet
in me? 

Thomas B