That shouldn't be an issue unless your work strictly prohibits 3rd party plugins. You can always append a folder to Maya's plugin path. I would find the location of the plugin, and then write a startup script or env file that adds that folder to the MAYA_PLUG_IN_PATH env variable so every time you run Maya it recognizes…
I dunno man... i like what you are trying to do, but i think you are still a little off on the dimensions of the scene, and some of your materials. I took some pics directly from the game. You can see more on the materials in the env, the kind of textures and mainly the spacing and depth. Your env seems really compact.
Good question, it really depends where you work and how they have their pipeline set up. Raven has Env artists who create assets and those who work purely in the level editor. The guys in the editor oversee the construction of levels and direct the assets being produced. While the asset Env artists make awesome shit. Hope…