What is the recommended way to model outer walls of an indoors level?

I am trying to port an architectural visualisation scene designed for static rendering from 3ds max into UE4 and I am not sure what is the correct way to handle the walls. The structure of the walls in the building is a bit odd (see image below). In the 3ds max scene the walls are simply modelled as a single mesh. That does not seem to be ideal for a UE level because the level needs to be navigable using a first-person controller.

I can think of 3 ways to handle this:

  1. Use the mesh as is with complex collisions
  2. Decompose it into convex fragments in 3ds max (this seems to be the way it is done in the sample scenes)
  3. Recreate it from scratch in UE editor using brushes

I was wondering if there is an accepted way to approach this? In particular if I try to decompose the mesh, how do I make sure that there are no visible seams in the UV maps and the lightmaps?