Load 16 sleepers (plus ECS loco) have been in Glasgow Central before, although it's a bit tight. However, the Sleepers are currently only Load 14 due to coaches being taken out for winter maintenance, so it's not a platform length issue.
As mentioned earlier, more passengers travel from Edinburgh generally, so if the Lowlander has to run as a single train, less passengers are disrupted if it's to and/or from Edinburgh.
How does it save money?
Just because the services don't run doesn't mean Serco gets out of paying GBRf, Alstom and all its other suppliers, or all the staff who aren't on strike, including the (expensive) management and 'back office' staff.
Then there's the costs of dealing with the disruption, processing refunds, informing passengers, handling complaints etc...
And for all this, zero passenger income (tickets or food/beverage) when the services don't run.
Erm... no.
All portions were due to run, with the Inverness diverted 'over the top' via Aberdeen. The cancellations tonight and on Friday night were/are due to the impact of Storm Arwen and services not being able to get through the (revised) planned routes due to blockages, OHLE damage, power cuts etc etc. Whilst some routes (but not all) are now passable, a lot of the stock is now way out of position - hence various empty stock moves tonight to get sets back to where they should be (although one of those has already had to be cancelled due to on-going disruption).