The guidance at http://wiki.openstreetmap.org/wiki/Railway_stations talks about disused stations, but I can’t see anything for stations under construction. Since a station is railway=station and a line under construction is railway=construction, there doesn’t seem to be an obvious way to tag them.
Also, should stations include things like “Station”, “Amtrak Station”, and “Monorail Station” in the name?
Both your station examples are wrong, for the same reason that it is normally wrong to do the things mentioned in your last paragraph. They all abuse the name to carry meta data, which should either be properly tagged, or, as a last resort, put in the description. (There may be cases were Station really is part of the name.) There is definitely a guideline that says names should not contain the type of entity, or, for things like chain stores, the place name.
http://www.openstreetmap.org/way/295728798 which is a geometrically better, but duplicate, mapping of the first example, is better, but still abuses the name to contain meta data.
I think I would go for construction=station, as construction=railway; railway=station, might get rendered ignoring the construction.
I’d definitely avoid tagging something that is not currently usable as a railway station as “railway=station”. For how to use a lifecycle prefix to explain the current state, see: