I would say the comment about drivers is rather unfair, 99% of groups have volunteers with no rail experience, when I started with my pres line I certainly didn't. People's issues aren't the types of people involved, more the lack of straight, honest answers and business plan. Blocking anyone who has a been open about there reservations rather than trying to reassure them is one massive red flag.
Most of us are guilty of saying the words "I wish xxx had been saved" and fair play to them they have gone to more effort than many about it.
Ultimately I can see the need to take on an entire unit being the groups downfall. As mentioned "modern" coaching stock on pres lines is completely different to "modern" units, to use the 315 as hauled stock is going to require major modifications.
Is it really worth it?
Depending on the which post you read the transport bill for 4 coaches is either 5 or 6 figures, then they have insurance costs and monthly rent.
Let's say it's the bottom end of 6 figures, £100,000, for the transport, from the sounds of it they don't have it, or if they do only just. Move all 4 carriages and there's nothing left for the other expenses. Save one or two carriages and there is roughly £75/50,000 left for the extra costs/upkeep, a serious amount of money.
I'd rather see a single carriage preserved in good, static condition, than a full dilapidated unit.