Graeme, The 1" Minnie is still proportionally a 1/12th scale engine, it is just not based on any particular full size prototype and the construction of some parts have been somewhat simplified to reduce the use of castings.
It still builds into a very nice engine and there is scope to add extra detail such as running boards, gear guards, dummy rivits to hornplates, etc. Although this one has been built to 2" scale it shows what can be done. And this album shows my Minnie, as you can see they are far nearer to scale than they are to Manod/Wilesco.
The other thing that the minnie has going for it is that castings are still available unlike the other options I listed which would require fabrication of carving from solid.
J