Speaking for myself, I couldn't imagine a wholly more boring subject for the basis of a model railways.
To me, model railways serve three key objectives:
Time travel - Perhaps it stems from me being a basher. But I’ve often remarked that as a frustrated 304.8mm to the foot modeller, given the opportunity, I'd forgo all railway modelling if I could time travel. First stop would be Crewe in March 1974, to catch 50 031 and 50 040 (Hood and my all-time favourite 'vac' Leviathan), over Shap to Carlisle. Nothing short of time travel, or the worlds most advanced form of matrix-like Virtual Reality could replicate that sound!
Exercise in Engineering - Alas, much like Dilbert, I too have been cursed with 'The Knack', and as Scott Adams once said "Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Probably why I gravitated to P4.
Artistic Expression - Hopefully fairly self-explanatory, but here is a quote for good measure "Art without engineering is dreaming. Engineering without art is calculating." - Steven K. Roberts
To me, the proposal of modelling a preserved line falls are the first hurdle. While, certainly you could model a preserved line at a given period, that period is unlikely to be of interest to me. Steam for the most part leaves me cold (blame working with steam in industry), and I like to wind people up be telling them I like exactly 1.5 types of Steam locomotives. the 1 being Black Fives, and the .5 being 9F's, because they we're practically Diesels I'm also far more interesting in the History of the working railway, something preserved lines always lack. As the a-typical anti-social Engineer, the appeal of something to move big chunks of coal and steel around, will always appeal far more than a line for tourists and the like.
As far as the second hurdle goes, preserved lines are often home to strange engineering practices. A prime example is the multitude of preserved Mk1 coaches, featuring a wide range of single phase electrical charging and connecting components, sourced from the local city electrical factors. White plastic just doesn't go with Chocolate and Creme, Blue and Grey or Blood and Custard...
Out of the three, Artistic expression is probably the only fence this horse would clear. But solely due to the fact that it contains the exercise of modelling a railway.
Regards
Matt