I'll go back to an earlier comment from Graham
"It seems like we have a triangle of conflicting requirements: Versatility vs Accuracy vs Cost."
I think there's another one which is just as important, especially when placed in context.
Versatility vs Accuracy vs Cost vs Interest
Interest is really important. Today there are fewer railway lines, in whatever country you live in, fewer trains, etc, but when the majority of correspondents on this site grew up in the 40s/50s/60s/even in the 70s, railways were a part of everyday life. They took us to school (the Steyning Stinker), they ran at the end of the back garden, we went on holiday in them, we took our dogs on them, we started trainspotting at 5yo and so on. Toots and whistles were in the background every day. We had to wait at the level crossing while walking home from school, we saw the signals go up - and go down after the train had passed. In some way, all of us had some kind of everyday interaction with the railway. We watched Railway Roundabout, we got the 'Trains Illustrated' and the 'Locospotters' Annuals for Christmas. There was no escape for our subconscious. We were interested in trains because they were there...they were in our blood.
Of course we wanted models of them, we wanted our train set, if only an oval nailed to a board, our imaginations did (and still do) the rest.
Today the kids only have us to remind them of these days passed. Who takes them trainspotting ? Who takes them on birthday outings by train? Who or what sparks the interest today?
The other day I was walking home from the supermarket and there was a mother and around a 4yo child on the footbridge over the railway. I asked after them, she said 'He likes trains and we came to the bridge hoping to see some but there has been nothing yet.' The time was 4.30pm. I said to them 'you're too early you need to be here between 4.50 and 5pm or so.' She said 'Why ?' so I explained ...'Well, at around 4.50 or so, after the Northbound express passes, you'll see the grain empties again, heading North - there are up to 4 engines pulling this train he'll love it, then you'll get the Southbound express and then steel empties heading South, again with 2-4 locos on, and then the Southbound stopper will pass by.' I also added 'If you come at 6pm, you'll get the long, loaded steel train, heading North which is about 1.5km long, then the coal empties for Metropolitan etc'. I see them there, at the appropriate time, 2-3 times per week now !! This child now has an interest.
Sorry, rambling, just saying....