Need help on my first project

Hi all,

I’m new to world machine, just bought it last week. I was watching several youtube tutorials any played around myself but couldn’t find something which helps me dealing with specific requirements of my very first project (a fictional map for a model train route). For you experienced guys this might be easy, thus I’m asking here.
What do I need? Here the specifications / needs, just putting them all together.

[ol][li]A terrain in size of 8x24 km (2049 x 6145 pixel) with hills, maybe rivers etc.[/li][li]
At each of the 4 corners I need an area of approx. 2x2 km which has to be totally flat without any changes in height (kind of platform). [/li][li]
From those platforms the terrain should begin to in- or decrease its height lightly in a natural way so that they don’t look like being glued or cut in the nature. [/li][li]
One of the hills / mountains should have a flat top (lets say 300x300m) where I could place an older castle on it later on… like for an place of excursions.[/li][li]
A bigger river (which could be used by ships) - water level for the map needs to be at 100m.[/li][li]
Some smaller platforms for building industries like forestry or alike on them (may in size of 100x100m) [/li][li]
Some hills / mountains [/li][li]
height ranges: 0-100m = water; 100-300m most terrain areas; 500-600m the top of the hill for the castle; 2500-3500m maximum height for other mountains…[/li][li]
height map for export… [/li][/ol]

The project will be just for my private use - I’n not planning to make it available to the public. So don’t fear that I could make your help / work available as being mine…

Any help is appreciated. But for interesting results / project files fulfilling the above I might spend some bucks to you if you are using PayPal…