Have you considered using the Slice modifier? It is a simple plane that can cut the model into two regions any of which can be made invisible by selecting Top or Bottom options. The plane can be moved or rotated in sub-object mode.
The modifier can be applied to a set of object as instances so you can just select the necessary objects and apply the modifier, adjust the position and orientation, select Remove Top or Bottom, then as a last step, use the Cap Holes modifier to cap the ends.
Hope this helps.
Edit: You can also consider excluding the shadow casting roof and necessary models to illuminate interiors. I don't know if there is any way to exclude illumination of environment GI, but you can try placing a sphere with a light material assigned to it, then you can assign your HDR to the light material. You might have to invert the normals of the sphere to illuminate inside it. Although it seems possible, I see a very apparent firefly type of grains with HDRs. I'm not sure how to manage that.
