How to handle a station that is both a source and a destination for a resource

There isn't any solution that I can see after puzzling over the image for a while. The only ones that would work would be splitting them by two tiles instead of just one and using a bypass track to get around it, but that would mean you're going up to 2 tiles of width anyway, rendering the issue moot.

The only workable idea that I can come up with is to set them as two different stations and use the "Non-stop" flag for the two different trains (train A to get it to ignore the first station, train B to get it to ignore the second station) but then if your trains happen to get out-of-order you're pretty much up crap creek.

I guess the only real answer is that there is no answer.

Assuming you don't want to break the station in to separate stations and use a load of feeder links, you will need to tweak the advanced option that limits your maximum station spread.

This advanced setting (specifically Stations→Max station spread) can be adjusted to values between 4 and 64, with a default of 12, and determines the maximum size square that can be allowed to bound each station (whether compound or not).

The recommendation is to only increase this if you are using the YAPF pathfinder, but this is the default so if you've never tweaked that setting there's no need to worry.

For more information, you can see the wiki entries for the setting and station spread.

If you need a station larger than 64 by 64, well then I think you're stuck (and possibly doing it wrong).