A fascinating variation on this would be for the stamping of the ticket to trigger the ORCATS revenue allocation, ensuring that the revenue went in all cases to the operator which actually carried the traffic.
I imagine a smartcard system would benefit from having validators on trains, such that boarding certain services (e.g. fast/intercity trains) would be more expensive than taking a slow metro/all stopper service.
This would then give passengers the ability to make a choice on how much to spend in 'real time' rather than having to plan in advance.
However, I'd see them more like the pink validators meaning they'd be required only to 'prove' your route, not to actually travel. You'd still touch in/out as normal (and be considered without a ticket for failing to do so) and just be charged the maximum fare if you didn't show you took a slower service that has a cheaper fare.
Ticket splitting would no doubt then cease to even be a thing, but for most people I think the positives would outweigh the negatives.
open boarding was a supposed reason to get rid of the bendies[1], then the new buses operate near enough the same system.
I expect it was an easier way to sell the removal of the bendy buses to the public, but we all know the key reason was that for many routes they were unsuitable and dangerous. I travelled on enough of them that clipped kerbs and mounted pavements when turning (sure, a lot of this was because of badly parked vehicles forcing bus drivers to do so) and saw - as a pedestrian - bendy buses coming very close to hitting people on pavements as a result.
Bendy buses are fine, in the right places.
Fare evasion was a major problem, of course, and may still be now, but that's really a secondary problem.
I don't think it's a bad thing we got rid of them in London, and doubt anyone really misses them. Certainly not people who found it hard to have to run way back to board a bus behind two bendies, and if you didn't would just close the doors and drive off. Again, because of other vehicles, it must have been a nightmare to line up to the kerb to let a wheelchair on in many places.