Gimp said:
When you add vehicles becoming invisble and not blocking line of sight so long as a unit leader is in base contact
This is only the case for figuring out the enemy's level of cover, and is *not* used to determine whether your soldiers can fire at them. If the unit leader cannot see the enemy, that miniature still cannot fire at the enemy - the vehicle is not "invisible" for that purpose.
I'm surprised this rule bothers you, as it seems perfectly realistic that if I'm hiding behind a friendly walker, it's not going to provide my enemy cover.
Also, you can't have your unit leader in base contact with an enemy vehicle - that's against the rules.
I meant it's wrong that they treat it as an area of terrain. Ohhhh, its all so confusing.