I know it'll be a while before a rail line is established, but no harm in talking about it.
I think Bla said he wanted to avoid a water crossing if he could, so I made this route and walked along it. The ice covered lakes are shallow, so no issue there. My thought is to go south through there, west through that land bridge, south under the plains and the swamp. Once it hits desert though, I don't know where it should go because I haven't decided on where I'd place a station.
Another option would be to go east instead of west at that lake and then go south. Going right through the lake could also be an option.
Also, I've spotted three cave openings in the southern part of the swamps, haven't explored beyond the openings. I assume cave systems aren't a problem?