1) If I have to restrict myself to only the built-in content, then I'm not going to bother. Most of the better stuff is not build-in content. The DLS content is touted as one of the biggest selling points of Trainz. Frankly, there just isn't enough usable content built-in to produce the sort of route I want to create.
...
3) I am attempting to upload the basic route only, without including any one else's content. If you check back a few posts, I gave a location for downloading the only non-DLS asset needed. This ought to be enough of a clue that I do not want to include other people's assets.
I sense some confusion. Whether or not assets are on the DLS or not has no bearing on this. When people are saying you should only upload the route, what we mean is you should be exporting and then uploading the route alone and none of the dependencies, regardless of where they come from. In other words, if you try to upload somebody else's content along with yours, the DLS will kick it out regardless whether that content is hosted on the DLS or not. No one is saying you shouldn't be using non-DLS content; I agree 100% that there's a lot of awesome content not on the DLS!

ETA: I sent you a PM.