Fertiliser Wagon
Accurate A class
CIE cattle truck
Proper AEC railcar
six wheel chassis at least, or ideally MGWR standard 6-wheeler.
That's all....
Once we have those, pretty much anything will be possible.
It's great to see freight wagons coming on so well. For years, we've seen increasingly accurate carriages, DARTs and locomotives, but goods stock seems to be poor relation.
In the 1970s, the only way of having Irish stock was to paint a Hornby Jinty in grey, or a Hymek in orange. The only way to have Irish carriages was to paint Mk 2s in either NIR maroon and blue, or CIE orange and black. Even now, many layouts have little choice but to have all the excellent Murphy and Bachmann locos and passenger stock, yet still repainted BR wagons!
Wagons are only just starting to catch up. For realism, the above half dozen items are so essential, that a layout based in the 1950-80 period simply is not realistic without whichever of those standards belongs to these various eras/