Regarding Nickl_C151's wish, I rather hope they will resume a
through train, but at a 30 to 45 minutes frequency. (Tanah Merah
shuttle remains) It will be better if there is a evening peak hours
crossover trains (7 trains from Pasir Ris will go to Marina Bay via
Jurong East then Woodlands)
You have to understand the rationale of starting the train from
Marina Bay. That area is where the IRs are located, most would
board at City Hall or Bugis, and some backpackers may stay in the
areas between Kallang and Paya Lebar. There are no major hotels
west of Raffles Place, hence it will be redundant to have the
airport shuttle travel that 20km extra.
At off-peak frequency, the airport shuttle may trail a normal
train 3 minutes behind. At peak frequency, they may follow a
schedule of 4+1, i.e. 4 normal trains before the airport shuttle.
Between 12 to 2 on weekdays, they may slot in the train such that
the schedule will show a normal train, lunchtime express, normal
train, airport shuttle.
Before you start bombing stuff like "there are many housing
estates all around", airport trains are only meant for the
conveneince of tourists. For locals, the only convenience they
should get is ease of transfer (a la Raffles Place, City Hall,
Bugis, Paya Lebar, Tanah Merah). Note that I did not introduce any
City Air Terminals as this airport shuttle I suggested will also
stop at all stations.