Interesting comment that night trains cannot be run without subsidy.
I thought that OeBB were managing to just about cover their costs with Nightjets, and I don't believe European Sleeper has any subsidy as such, though maybe it's burning through investment money - time will tell.
It is perhaps relevant that European Sleeper runs almost entirely couchettes which must help with numbers. But it also suggests that there is still a market for traditional couchette travel as well as the one or two person sleeper with ensuite and shower etc.
I would love for us to get sleeper services to destinations like Berlin or Barcelona from St Pancras, and if the trains had airline style first class seating for standard class, that are open but still provide some privacy and a seat that turns into a bed, you could fit a lot more people on. First class could be a traditional cabin, and by all means have open areas for people who are happy to save money and sit in a basic reclining seat all night. I wouldn't be a fan of the pods that you slide into, but I expect they could be considered for part of the train too (I do wonder how they'd be considered if there was a need for an in-tunnel evacuation though).
Trains could split when they arrive in France to give two destinations from one train starting in London.
There must be stacks of capacity in the small hours for such trains to run, and there wouldn't be the usual capacity issues at St Pancras beyond the need to have border staff work a bit later or earlier (but by how much? Chances are the train would leave around the same time as the last Paris service anyway).
I expect the cost of new trains is the barrier here, and there's the perception that will tell a lot of people that it's so much quicker to fly that nobody would ever bother to take a train. Well, I for one would because when I go to places like, funnily enough Berlin and Barcelona (hence my examples) it either requires trying to go to bed early and getting up at 2 or 3am to get to the airport for an early flight - which invariably means getting almost no sleep and having to pay for a taxi or peak fares to the airport OR you go the night before and stay in a hotel at the airport, which isn't often cheap.
So I'd sooner get on a train in the evening and relax, and if my space was designed well enough that I could sit and watch my phone/tablet/laptop until I felt tired, I'd barely feel like I'm travelling at all. When I wake up, there's no going to an airport for an early flight - I've already arrived.
Europe seems to be going all in on sleepers to reduce flights, so it's disappointing that we're not really interested.
Obviously engineering work is a factor when running services through the night, but I'd assume that if Europe is getting onboard with sleeper trains then they're already working on how to manage that. At the very least, long term works can just mean certain trains not running, or partly run with coaches if people would be happy to have that option over no train at all.