Hi Erik,
Visual identification of wall location lines and interior/exterior edges is something that has been waited from a looooong long time !
Why is it needed for you asked ?
For QA/QC checks of model consistency off course ! BIM is all about data accuracy throughout exchanges of a same model between parties and ability to foresee the consequences of unforeseen changes !
Ok, but what's the problem with the actual behavior you'll ask ?
When you're changing the thickness of a concrete wall around egress path, a stair or lift shaft for example you never want to have the walls be widen toward the center of the room and create either a egress regulation issue or a clash with the Lift moving parts ! The same apply if you've got technical rooms with specific internal dimensions requirements or external walls that have to stay into the property boundary, ...
Of course we could expect that the modeler always chose the expected alignment and drew everything clockwise with interior of walls facing the interior of rooms... but what if he didn't ? Which side of a wall has to be "interior" when there are 2 rooms with a same functional requirement ?
The problem is that now we cannot control or get an idea of the consequence of a wall thickness change without having to do it by selecting the walls one by one and tryout !!! That's a tedious and such unproductive workflow which could be really easily avoided because the information is already there in the wall... it's just invisible !!
The same problem occurs if we have to add a finish layer to already modeled concrete walls. Because they have just one structural layer of one material, it's impossible to know in advance which side will receive the finish, and which walls will have to be switched. (I already used the trick to add a 5mm red concrete layer on the interior of my concrete walls and remove those 5mm on the structural layer but then my wall properties/quantities are wrong ! Placing a membrane layer on the outer faces of a wall being forbidden by Revit, I had no other choice...
)
You (Autodesk) just have to add 3 new subcategories to the wall categories.
Just as we now have a "Common Edges" subcategory, we should also have the "Interior Edges" and "Exterior Edges" subcategories to be able to give specific colors (e.g. in coarse views) to those faces whatever the layer function they have.
AND we should also have a "Location Lines" subcategory just as it already exist for beams.
BTW, if you are in changing that for wall components, it would also be good to
_ add the possibility to place a membrane layer on the outer sides of walls (like bituminous paintings or dustproof/primer paintings which should not get a thickness value but should be visible in 3D) AND give the ability to override this membrane layer Line style through the "VV -> Override Host Layers -> Host Layer Line Styles" dialog !
_let us control the visibility of each layer by putting those as subcategories or by placing a "visible" checkbox in the "VV -> Override Host Layers -> Host Layer Line Styles dialog" ! --> this is really needed for coordination of Concrete Structure models with Architecture models containing multilayered walls !