Usually as an end to end journey on steam special to enjoy the scenery. Not to go traipsing off at Appleby to take a ride on an ex Southern DEMU for 6 miles.
I share what Yorksrob said and pick up Steam. You dont think for one moment, the EVRT would be a one trick show pony with "just" Southern DEMU's do you?
I think having visited the site a few times over the years, that they lack some covered storage.
Once they nailed this bit, they'd appeal to smaller loco owners which would be very suitable for that line.
You are entitled to your opinion, but as a businessman myself it usually starts with the dream and a touch of optimism to launch things, then you can start discussing realities needed. If you are an eternal pessimist then you will never ever get past first base!!