I'm not trying to shoot you down & I have no intention to
(I'm going to try to put it to you in a nicer manner than
'SBS6078M' in case you shoot him too), but the reason why 36 is
making do with its fleet of KUBs (majority Euro Vs somemore) is
because the crowds along certain sectors of its route is really
really heavy. The Suntec-Orchard area is one, the Marine Parade
that area also.
If 36 gets Citaros, yes it will be faster and less lethargic on the
expressway stretches. But the time made up on the expressway
sectors would be lost once you hit those bus stops with such heavy
pax traffic. The KUBs are just faster in loading everyone onboard
to be honest due to its wider aisle and larger standing area below
the steps. 
The higher roof of the KUBs also makes it easier for the BC to see
if there's any alighting pax who is trying to get out but stuck in
the bus. I've encountered many BCs driving the Citaros which are
packed who either: 1) Missed the stop where pax already pressed the
bell long ago (no 'Stopping' warning light on dashboard for
Citaros, KUBs have), or 2) stuck at the bus stop for twice the time
needed in a KUB because everyone's head is blocking the BC's view
of seeing who exactly haven't alighted. And yes, that is with CCTVs
fitted at the same positions as the KUBs on the
Citaros. 
And if I'm not wrong (I'm not too sure about this), but the KUBs
are more suitable for 36 too because 36's rest time at CGA (that is
its only terminating point) is slightly shorter than the other
airport services with Citaros (24 at AMK, 53 at Bishan). Not to
mention the jumpbus system of 36, the BC of the previous 36 bus
usually jumps straight onto the next 36 bus that arrives around
5-10mins later to take over & drive straight away, rest for the
BC yes but no rest for the bus practically. You probably won't feel
it from inside or outside the buses accurately, but the Citaros
actually run hotter than the KUBs. That's why if you put Citaros on
36, they might tend to overheat faster? 
Ok, maybe you have your points.
But in the past, B10Ms are able to deal with the crowds as
well.
Maybe 39 should get some Citaros then. 
