Only possible for the 2 pairs of Exit in the middle like KMB's
NAC 3-doors DD in the 80s/90s...
If a stronger engine body
frame to hold the engine like Borismaster, but aircon system would
be a problem as to where to place it lets say the 3rd-door is the
same as Borismaster...
AC system could be roof mounted (which is done on the NBfL), but
it is still not possible unless it is a hybrid.
NBfL could do this because the engine (generator) is not
directly linked to the axle, and technically the bus is mid/side
motored since the electric motor driving the bus is infront of the
rear axle.