For me, take the single decks off the x93/4 all together. Only use for emergencies like high winds. Or last minute breakdowns.

New MMc at least 9 would be great.
Keep 2 or 3 b9s for the park and ride.

Scrap or sell off the rest of the deckers currently in place.

In terms of the 95/6 invest in some new style front wheeled drive mini buses.

X4 new buses again with 6 cylinder engines