How do I build lengthwise multi-platform stations?

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.

There are some tricks for elongated stations, though no designs I know of are actually only a single-tile wide. Here's a basic implementation of the principles with a 4-tile wide double-direction design.

You can halve this design to get a 2-tile single-direction station.