Yeah, but you, I, and the fly on the wall all know that won't happen. So much work to preserve a very dated walk through?
Well, the blue "redirected river" wouldn't have to happen to make the plans viable. The yellow "expansion area" could just take place in the existing land around the north side of the river. It would be a lot of land to develop, but the flip side is that a lot of new land would be developed and able to be utilized -- a potential benefit for a park getting as high crowds as MK. Plus, more guest flow options, especially during the parades, and a removal of a dead end in the park.
The beauty about train tracks is that they can easily be moved . Honestly, you wouldn't even need to move them all that much. There would be a point though where the path would have to travel back under the track, like it does already in the splash/thunder mountain area.
Yep. The train in that area would have to be closed at some point to accommodate the build, but it could happen and could be used to have a new attraction "interact" with the train like Splash does. Also, it might be an opportunity to actually add a scene to the train ride like the dinosaur/Grand Canyon ones at DL (wouldn't a Grand Canyon diorama be perfect as you pass through Frontierland on the train?).
It's worth noting that Hong Kong has lands explicitly outside the railroad track berm. No reason it can't be done at WDW.