If it is going down 104th Ave., then it makes sense to me to install a wye at 104th rather than looping back up from King George Station.
That would leave the tail track at King George Station available to head south down King George Highway.
That would be feasible (it was done for the M-Line) and the interruption (using longer trains running on single track while the other is reconstructed)
would only affect Surrey Central and King George Stations.
In order to serve Surrey Central Station area, there would have to be a station on the 104th line at the wye (i.e. at King George HIghway)
or, as Cornholio mentioned, have the wye south of Surrey Central Station (which would make for curvey detour on the line).
As for whether Skytrain is appropriate for Langley - if Surrey City Centre is to be the next downtown in the regional - as big as Vancouver -
then it makes sense to view the Expo line as feeding Surrey City Centre, not just feeding Downtown Vancouver.
I do agree it would be a long ride from Langley to downtown Vancouver.
Here's a good Global Air Pic of the area showing the hydro ROW and the SUrrey Central Station area and 104th Ave.
And here are my suggested allignments - I prefer the red line with a station at King George Highway.
If Surrey orients its transit (bus) plaza between the two stations, it would work OK and transfers from Guildford to King George could transfer at Gateway Station.
I suppose there could be an issue though with bus passengers having a choice of two nearby stations (esp. if one branch has more service than the other).
The blue routing would focus a lot of passenger traffic on Surrey Central Station (possibly overloading it in the long term?), plus the red routing allows more stations in
a more central location in Surrey's downtown than the blue line (which is further to the south closer to King George Station).
As for the overpass, Skytrain can make sharper turns than the Canada Line trains, so the structure wouldn't have to be as massive as at Bridgeport Station
- think Columbia Station-Skybridge switches.