I'm so sorry it's taken so long to respond to all these messages - I think it just goes to show this is a very diverse hobby, everyone seems to do everything slightly differently, there is rarely a 'one size fits all' solution - which I like
I'm going to go with Maxi's advice - thank you very much, especially for contacting Roundhouse directly that was very kind - and create a translator wagon for now. I acquired a lot of the LGB rolling stock before I really knew what I was doing and I think over time I'll end up replacing it with more detailed, and layout specific rolling stock, slate wagons and tipper trucks as I'm building a mine complex as part of the landscaping. So I'll defer a long term decision on 'coupling' until I've got a better idea of the rolling stock I'll be using long term.
My other engines already have LGB style couplers and I've just started converting them to battery RC so that's another learning curve...
I think an important point someone made is that it depends on realism over practicality, my layout is very much an extension of a landscaped garden - so a garden feature - albeit quite large - I've got no real specific style in mind - although it's loosely based in the Scottish Highlands - hence the 12 tons of granite so far...
I really just want to be able to sit in the garden, reading a book, and watching trains go by...
One day
Thank you all again for the fantastic advice - I'm sure I'll be back for more soon!