Evasion as a mode of defence is an interesting concept, but currently in the game it seems to be barely implemented. There is no extended tech tree and stacking of evasion modules is not permitted. 

However, I think with some fairly simple changes to the math, we could have evasion as a fully-fledged defence mechanism.

Let's say evasion modules produce evasionPoints. There is no stacking limit: just add whatever evasionPoints you get from the components and techs and percentage bonuses, etc. So say bombers get a 50% bonus on evasionPoints. Let's call the fraction of the time that a weapon misses due to evasion as the evasionRate.

evasionRate = 100% * ( 1 - hullSize / (hullSize + evasionPoints))

In this model, you need to stack your hull size worth of evasionPoints to achieve a 50% evasionRate. You need twice your hull size of evasionPoints to achieve a 67% miss rate. In general, you have to dedicate a fraction of your available mass to evasion modules if you want to achieve a good miss rate.

If you want a race between sensors and jamming (like there should be a race between weapon damage and armour/shields), then you could have tech or weapons come with a percentage bonus that works against evasion. Let's say a trackingBonus as a percentage, that can go as high as you want.

evasionRate = 100% * (1 - (1 + trackingBonus/100)*hullSize / (hullSize + evasionPoints))

trackingBonus would either be it's own modules or tech bonuses, or innate like the frigate module. If it scaled with tech, you'd have a race between advancing jamming tech trying to drive hit rate into the floor and advancing sensor tech trying to drive evasion into the floor.