Models have stats so that we know their game effects. I would propose doing the same for terrain. Here is my suggestion for putting attributes/stats onto terrain: (this covers movement as well as cover. I also used a lot of SSTV1 ideas)
Terrain pieces can have 3 different effects. The effects are Movement, LOS, and Protection. Each effect has a size value associated with it.
Terrain effects stack.
A model may gain only 1 form of save bonus.
Players should agree on terrain effects before the game starts.
Movement
Difficult
The distance to move through Difficult terrain counts double.
Models of size greater than the Movement effect Size ignore the effect.
Impassible
Impassible terrain cannot be occupied or moved through by models.
Models of size greater than the Movement effect Size ignore the effect.
Impassible becomes Clear with the Climb special Movement
Water
Water terrain counts as Impassible, though it can be overcome by abilities, e.g. Flying, Water movement, etc.
Models of size greater than the Movement effect Size count the terrain as Difficult.
Models of size twice the Movement effect Size ignore the effect.
LOS
LOS is determined by tracing model center dots.
Model location is determined by the model center dot.
Obscuring
Obscuring terrain takes effect when a LOS traces through or into obscuring terrain.
Targets of an attack affected by Obscuring terrain enjoy a +1 Obscurement bonus to their Save.
Models IN Obscuring terrain do not get a save bonus if their Size value is greater than the Obscurement effect Size.
Example, a Marauder(Size 3) is not obscured in Size 2 or Size 1 Obscuring terrain.
Intervening Obscuring terrain (where the LOS goes through Obscuring terrain, but the target is not in Obscuring terrain) does not take effect if the Size difference between the models tracing LOS is greater than the Size of the Obscuring effect.
Example, LOS between a Warrior(Size 2) and an LAMI trooper(Size 1) is obscured by Size 1 or bigger Obscuring terrain, giving the Warrior a +1 Obscurement save bonus.
Models may trace a LOS into and through obscuring terrain up to the twice the size of the target model. Remember that the size difference may cause the Obscuring terrain to not have any effect, see above.
Example, LOS from an LAMI trooper(Size 1) may cross 4 inches of Obscuring terrain to a Warrior(Size 2).
For an acting model in Obscuring terrain, the Obscuring terrain does not take effect for distances from the acting model up to twice the Size of the acting model.
Example, an LAMI trooper(Size 1) may Shoot up to 2 inches out of obscuring terrain with no Obscurement effect.
Example, a Warrior(Size 2) being shot by an LAMI trooper(Size 1) 2 inches away in the same Obscuring terrain does not get an Obscurement save bonus, since 2 inches is within twice the size of the LAMI trooper.
Blocking
A LOS may not be traced through Blocking terrain.
Blocking terrain does not take effect if the Size difference between the models tracing LOS is greater than the Size of the Blocking effect.
Example, LOS between a Warrior(Size 2) and an LAMI trooper(Size 1) is blocked by Size 1 or bigger Blocking terrain.
Example, LOS between a Warrior(Size 2) and a Grizzly Exosuit(Size 2) is NOT blocked by Size 1 Blocking terrain.
If the size difference of the target and attacker is only 1 greater than the terrain size, the target enjoys a +1 Obscurement save bonus.
Example, Size 1 blocking terrain between a Warrior(Size 2) and a Grizzly Exosuit(Size 2), allows the Warrior a +1 Obscurement save bonus.
Protection
Model location is determined by the model center dot.
Protection has facings, e.g. protection may be all around(like in a fort) or from 1 direction(like a wall)
The effect takes place when a LOS traces from outside the terrain into the terrain in the direction of the protection.
If the size difference between models is greater than the size of the Protection, the Target gets a Protection bonus only if the Protection protects the top.
Light Protection
Models in the terrain get a +1 Protection save bonus to their saves.
Heavy Protection
Models in the terrain get a +2 Protection save bonus to their saves.
Terrain examples:
Light Wooded Area
Size 2 Obscuring LOS
Muddy Terrain
Size 2 Difficult Movement
Smoke
Size 3 Obscuring LOS
Smoke on top of Muddy Terrain
Size 2 Difficult Movement
Size 3 Obscuring LOS
Large Stone Structure
Size 4 Impassible
Size 4 Blocking LOS
Water
Size 2 Water
Foggy Lake
Size 3 Water
Size 2 Obscurement
Heavy Wooded area
Size 3 Difficult Movement
Size 4 Obscuring LOS
Size 3 Light Protection
Fortification
Size 4 Difficult Movement
Size 4 Obscuring
Size 3 Heavy Protection
Bunker
Size 2 Difficult Movement
Size 2 Blocking LOS
Size 2 Heavy Protection All Around and Top
Simple wall
Size 1 Obscuring LOS
Size 1 Heavy wall (The definition is complicated, but players will easily understand what the effects are)
A Heavy wall would be 2 overlapping terrain areas.
Size 1 Heavy Protection in the wall direction in a 1 inch area on one side of the wall
Size 1 Heavy Protection in the other wall direction in a 1 inch area on the other side of the wall
Mwahahah! 
