My guess would be that to keep construction costs down and increase passenger capacity there will be a reduction in the number of berth cars and an increase in the number of seated cars with pods/cradles.
At the moment I believe the format is something like:
- Glasgow 6 sleepers 1 Lounge 1 seated/brake van
- Edinburgh 6 sleepers 1 Lounge 1 seated/brake van
- Inverness 4-6 sleepers 1 Lounge 1 seated/brake van
- Aberdeen 4-5 sleeepers 1 Lounge 1 seated/brake van
- Fort William - London 2 sleepers
- Fort William - Edinburgh 1 Lounge 1 seated/brake van
Giving a total carriage nightly usage of 66 vehicles with 9 spares for a total fleet size of 75 (53 sleepers + 11 seated/brake + 11 lounge cars).
With the new pods/cradles I'd expect the Seated Sleeper to Fort William to run directly in future. For operational simplicity you might well decide to sacrifice Aberdeen - Inverness capacity/flexibility and just run a four coach rake all the way from Fort William to London both ways each night.
This is particularly likely as the tender mentions with regards to luggage:
Sleeper Franchise ITT said:
Luggage and cycles should be able to be transmitted to the passengers destination station without further action by the passenger after initial storage.
And couchette passengers:
Sleeper Franchise ITT said:
If Bidders are proposing couchettes for budget passengers in response to Section 4.1.2.1 (Rolling stock strategy) of the ITT, then they should not expect passengers to have to change location during their journey. Recognising that the Fort William service also provides the first and last service, we would wish budget passengers not to have to change location either. However if for operational reasons a change of location is required then Bidders should set out their reasoning in their Delivery Plan.
Assuming that platform lengths at Euston restrict operation to 16 car trains you might expect the future usage to be more like:
- Glasgow 1 Business Sleeper 2 Standard Sleeper 1 Club Car 3 seated pods/cradles 1 seated pods/cradles with cycle/luggage space
- Edinburgh 1 Business Sleeper 2 Standard Sleeper 1 Club Car 3 seated pods/cradles 1 seated pods/cradles with cycle/luggage space
- Inverness 1 Business Sleeper 2 Standard Sleeper 1 Club Car 1 seated pods/cradles 1 seated pods/cradles with cycle/luggage space
- Aberdeen 1 Business Sleeper 2 Standard Sleeper 1 Club Car 1 seated pods/cradles 1 seated pods/cradles with cycle/luggage space
- Fort William 1 Business Sleeper 1 Standard Sleeper 1 Club Car 1 seated pods/cradles with cycle/luggage space
This gives a fleet size of 64 made up of 10 Business Sleepers, 18 standard sleepers, 10 Club Cars 16 seated pods/cradles 10 seated pods/cradles with cycle/luggage space.
The extra 8 cars (to fit the 72 ordered) would be 1-2 x spares of each carriage type with a total order of:
- 12 business sleepers
- 20 standard sleepers
- 11 Club Cars
- 18 seated pods/cradles
- 11 seated pods/cradles with cycle/luggage space
This could keep the construction costs low as you are only actually building 32 specialist sleeper carriages along with 40 fairly standard railway carriages fitted with fairly standard airline/ferry seating.