Yes, I'm really impressed too with what you have achieved with my very limited (at present) assets. I have a page of possibles which I scribbled down yesterday in an odd moment. They will all be scaled up versions of my own already uploaded content, of course, or items made for the purpose.
I'm going to try track already raised to the required 6 metres later but this neans of course that any "bulk replacement" of existing track will (if successful) float 6m above track already laid! But you've obviously managed to cope with the oddity so far. Still, there's always the possibility of another garden ... I must have a go sometime - it's a long time since I was able to do any "real world" gardening.
And then there's 0 gauge and N gauge to think about ...
Incidentally, I also made a good few models some time ago in 1:12 scale, ie. models which are 1 inch to the foot in Trainz, with a view to making a model village for Trainz tourists to walk around. I don't think these were ever uploaded. I suppose 1:76 scale models in Trainz could also be made, but could they be seen?
A final thought - maybe my track on viaducts (quite an extensive system) could be used in the garden, too, either on it's own or to link sections?
Ray