Should Certain Trains have Ticket Machines or Sales On-board?

[RailWonderer]

As a spinoff thread from this one,

Should Every Station (& every Platform) Have a Ticket Machine?

Some stations are located in very isolated places so those machines could be liable to be opened up by thieves.

www.railforums.co.uk

I had the idea that some guard operated trains should sell tickets on board in exchange for a permit to travel and cash/card payment instead of having a machine at a station in order to cut costs of installing them. I'm thinking of desolate or little used stations where the trains that serve are often not DOO and have guards on board to serve customers. If the guard has not the time to sell one or refuses for union reasons, a permit to travel ticket and cash could be exchanged for a ticket on a machine installed on a train.
I think this has come up before but was not sure what the consensus on the idea was.
Ideas? This is common in Europe but not the done thing in the UK - with reason?

 

[DelW]

As a spinoff thread from this one,

Should Every Station (& every Platform) Have a Ticket Machine?

Some stations are located in very isolated places so those machines could be liable to be opened up by thieves.

www.railforums.co.uk

I had the idea that some guard operated trains should sell tickets on board in exchange for a permit to travel and cash/card payment instead of having a machine at a station in order to cut costs of installing them. I'm thinking of desolate or little used stations where the trains that serve are often not DOO and have guards on board to serve customers. If the guard has not the time to sell one or refuses for union reasons, a permit to travel ticket and cash could be exchanged for a ticket on a machine installed on a train.
I think this has come up before but was not sure what the consensus on the idea was.
Ideas? This is common in Europe but not the done thing in the UK - with reason?

To name but two, the Cambrian Coast and the Heart of Wales lines have guards selling tickets. Both lines have plenty of request stops that have no facilities beyond a platform and a small shelter, so it's the only way most passengers can pay cash for a ticket.

 

[jacobmartin]

I think they should have some ticket machine on board.