Silly question - how many customers actually want to arrive in London before 07:00 anyway?
Not many.
In fact with delay repay I expect most would be pretty happy.
Not ideal for passengers joining at stations enroute of course, but hopefully they would all be understanding of the reason.
Given the economics of sleeper services would it be justified to modify their delay repay conditions?
It's awkward as some may be heading for onward connections and need that early arrival time - but their needs may be better met by them having travel insurance to cover disruption, which might meet the actual costs they may incur.
The Paddington arrival being ~05:04 and cabins to be vacated by 06:45, if
GWR▸ honours delay repay on the basis of that 5:04 arrival there must be many many travellers who'd regard anything before a 6:45 arrival as meeting their needs (and quite a few who'd be fine with 8am but of course Paddington needs the platform...) If, on the occasion that the service arrives an hour down, GWR are meeting a lot of delay repay claims on the basis of that 5:04 arrival it might be that they're compensating some for the hour or more that they'd have spent snoozing anyway.
More relaxed arrangements for delay repay on sleeper services might be for the general good as long as the railway doesn't then regard itself as deincentivised to run the services to time - but again, the avoidable costs involved in tying up a platform in the morning peak should address that.
Mark