If part 2449 existed in original brown, I think it would be a nice addition as shown in the PDF instructions. Regardless, I have come to the conclusion that it never existed and therefore replaced it with the reddish brown variety.
For whatever reason, I like to build models in their entirety before making modifications, but I really don't see myself making many modifications to the exterior of this model. In my opinion, this MOC is truly exceptional for the following three reasons:
1) Size (obviously) - it's essentially a massive canvas that Cavegod has done an amazing job filling up
2) The balance struck between the shiny flat brick/panels and the intricate greebling - we see this in other models, but rarely does a model create this effect from so many different angles
3) The use of the three different browns (as well as the normally occurring variants within reddish brown) - besides providing for a certain authenticity, it creates another level of depth that is difficult to produce
I am really enjoying the build, though I will admit I am looking forward to regaining some space for other projects when it is completed!