It's a weirdly circular argument though, isn't it.
Subsidy is too great because train is lightly populated, therefore fares have to be high, therefore selling it as a premium product and pricing regular travellers off the service, therefore subsidy is too great.
At a rough mockup of a Mk5 carriage (carriage is to scale, internals are somewhat imagined based on the above).
Standard configuration has a minimum of 10 passengers, all in solo berths, or a maximum of 20 passengers, all in twin berths.
The rough sketch I have done, using S shaped beds as suggested above, has a lower maximum of 16 berths, 9 single berths, 3 twin ensuite and 1 solo ensuite.
However, minimum is higher, at 13, 9 single berths, 4 ensuite berths.
Presumably CS' calculation is that the higher overall potential capacity gives them greater flexibility long term.
Personally I would say the direction of the travel / hotel industries is going in the opposite direction.