Forget the portion, just run it later so it arrives at Plymouth at a reasonable time and market it as an option for business travel to the Southwest.
I take the point about the Scillonian but it only runs for 8 months a year and I'd be interested in the details of numbers of customers who use the sleeper specifically for that purpose.
As well as the Scillonian, there's a few potential issues that might cause problems if you did that:
1)
AIUI▸ the three customer hosts who work the sleeper service do so throughout from Paddington to Penzance. That's already a long shift and it probably wouldn't be possible to extend those shifts by two or more hours. So there might be extra costs providing two sets of customer host crews.
2) Not sure what the
TM‡'s and Drivers do, except that they change over at Exeter, but again 2-3 hours later into Penzance might mean more crew are required overall depending on what trains they work next.
3) Passenger trains leave Plymouth for Penzance at 07:12, 07:43, 08:08, 08:47 and 09:15. Given the signalling headways on the route there is no room for another one, so one would have to go and I doubt that would be popular amongst the good folk of Cornwall. You'd be looking at a Penzance arrival of around 10:00-10:30, with the first day time train from Paddington arriving not too long after at 11:40!
At the moment the sleeper is run largely on whimsy and subsidy at a time when the railway needs to save money and/or look to increase revenue. This would seem an opportunity worth investigating.
I have no idea whether Plymouth MPs▸ are lobbying for it. I suspect that it's been so hopelessly impractical for so long that people/business just gave up and drove/travelled elsewhere and it's not talked about much.
Sounds like the sort of thing one of the local MP's would love to crow about achieving, and if the extra stumbling blocks above can be overcome, perhaps it's worth you (or a friend who still lives in one of the constituencies) from writing to them to suggest?
This may be a way to get more people on the trains which I thought the majority of those on this forum were keen on?
I'd be delighted if the
DfT» funded the extra costs that would result from either a long layover at Plymouth or a second portion being detached. However, that needs to be balanced with the clear intention of the DfT to reduce costs, not increase them, as evidenced by the quite severe cut backs in rolling stock that
GWR▸ are permitted to use. Costs seem much more important than any revenue growth at the moment.
For that reason I personally think it's a bit of a non starter sadly.