Here are a couple of ideas about your proposal to do a Royal Gorge route.
First, do it in more than one section. If I were doing it, I'd use at least five sections: Pueblo to Cañon City; Cañon City to Salida; Salida to Gunnison, Gunnison to Olathe, and Olathe to Grand Junction. On a route this size, if you get tired of working on one section (or run into a problem you're not sure how to solve), you can move to another one.
I was going to start another thread for this next idea, but instead I'll take advantage of the opportunity to publish the idea in this one.
Second, while this is, at least as far as I know, a novel idea, I'd do a lot of the work in Blender. I have proven to myself that one can create a surface using Blender upon which one can install track, and which one can texture, and one has much greater control over the surface with Blender than one has with the topology tools in Trainz. Further one can combine many blender objects into the scene. If you're doing buildings, place them on the Blender baseboard; when you get the board completed, export it to trainz, and place it intact on the baseboard. This will have the added advantage of giving you capabilities that are missing in Trainz. For example, the topology tools in Trainz do not permit a vertical, or undercut terrain, but you could do that without too much problem in Blender, and since when imported, Trainz will see your board as a structure, it will not complain about such things as balancing rocks, vertical walls, and undercuts. Further, because you can subdivide and sculpt blender regions, one can get much finer geological detail with Blender than with TS surveyor tools.
It's not quite as hard as it sounds. If one exports the default blender cube, and imports the mesh into Trainz, the default cube is the size of the large original squares on the Auran baseboard. It's easy to start a baseboard: delete the top four vertices of the cube, and scale the resulting plane face by 360 units in the x and y directions, and one has a 720 x 720 surface.
[Note: Even though I've already got my flame proof suit on, I would fully expect that one could use 3ds Studio to model the route just as one could with Blender. I'd be surprised if one could not do it with GMAX, too, but I've very limited experience with that software, and it's not at all current. I'll leave it to others to confirm or deny the viability of using GMAX.]
By the way, it occurs to me that creating a baseboard in Blender also provides a solution to the request I made for route rotation capability in the Suggestion Boxcar forum. The Trainz baseboard, and any content referenced to that baseboard, can stay in it's native orientation, but one can rotate the surface, and any content fastened to the sufrace, that us created in 3d modeling software. There is another issue that this technique can address, which is an old topic in the Suggestion boxcar. One can create a portion of a board in modeling software, too, satisfying those who would like to have a triangular shaped board to fill in with. Also, for those interested in producing free-lance routes, the technique can be used to prototype the route, with more precision and control than one gets from the topography tools in TS.
Finally, a last suggestion for the Royal Gorge route: invite collaborators. if there is one other person interested in participating, you halve the work you have to do; if there are three other people, you cut the work you have to do in half again. And working with them would not only speed up the work, but provide an opportunity to work with like minded men and women. And you'd certainly have to have at least one field trip, too, providing a chance to get together with friends and enjoy a common endeavor.
ns