The Idea: Instead of constructing by building per tile from station to station one would only virtually build and terraform in some sort of sandbox while the game is running and at the end submit the whole "plan" to the server. Everything would then be constructed at once. I imagine there could be several levels of realism, possibly set as server variables- for example construction time.
What's the point? Well, first off you can plan without burning any money. If you're a start-up company you can start as big as possible and see if you have enough money to finish beforehand. If not, you can optimise your layout by reducing costly terraforming, brigdes or amount of tracks.
Financing: The financing system could become more of an integral part of the game as you'd have to pay per project and not per constructed tile. This could serve to make the game more realistic and include more banking options. Imagine fronting some part of an expensive project and pay the rest after construction or maybe include special loans.
Multiplayer: I hope (please share your views on this) it would greatly reduce the amount of sabotaging as you can't be caught in the act of constructing. No-one would see your plans until they're submitted and then it's "first-come, first-served" . One could also imagine some kind of "global authority" or simply a vadility check on what you submit. You'd only be able to submit projects that actually connect two or more stations. You wouldn't be able to just build a piece of track or terraform somewhere without purpose.
Improvement: In TTD a lot of time is invested in improving your existing networks. Imagine planning major reconstructions without stopping your traffic. When you're done, you submit your project and everything is constructed at once. Well, with the set construction time depending on how realistic you want your game.
Additional restrictions: I'm not the author of the following idea, credit goes to whoever had it first. Sorry, I don't remember who exactly- I read it here a long time ago. I imagine it would be easy to force a player to terraform realisticly by making sure the amount of land raised equals the amount of land lowered per project submitted. One could also have an option to restrict the distance one can move a certain mass of land, although that might be hard to implement.
Problems: My own constructive criticism, I'm sure you have a lot to add. In my head I picture the planning phase as kind of translucent overlay to the real map. In coop games one would have to have the option of somehow sharing ones construction plans or working on them together. Additionally there would have to be some kind of local authority visualisation if you try to submit a project and one or more towns don't like it. Maybe the areas in question could be highlighted in red or so. Then again it might be an advantage to plan around those things without wasting money first. There'd also have to be an option of saving construction plans as one usually spends a lot of time on them.
Constructive criticism and ideas on how this could be made more realisic both in terms of gameplay and implementation strongly encouraged
