3D Terrain Modelling of World Map for a game / GIS (See job description)

Hello,

I am working on a strategy game in Unreal Engine. My overall object is to make a game similar to:

https://store.steampowered.com/app/268890/Masters_of_the_World__Geopolitical_Simulator_3/

As you can see it is a point and click game, played on a world map, and each player chooses a country to play as.

I require a similar world map to be made. The specifications I want the map to be made too are as follows:
- Each country will be its own individual mesh, and each country will be made up of States or Regions or Countries as individual meshes. (See Pic 1 & 2 for meaning of states/regions/counties).
- The map should have a heightmap version (elevation levels) and a flat version (like in the above game example).
- The map style that I would like to achieve is (But flat instead of sphere):
https://unofficialnetworks.com/2014/06/10/detailed-relief-maps-show-worlds-mountain-ranges/
- The world map should come textured.
- The project should be delivered in a .blend file
- While considering the below, please let me know the recommended size/scale of the map you can produce this in.

On top of this, I am unsure if the following is possible.
I would like some GIS data to be placed on the map, but instead of actual roads, buildings etc, I would like 'placeholder', which can be simple meshes that are just marking the location of that object. The reason for this is that these placeholders can be replaced inside unreal engine with a suitable mesh.

I have not set a budget as I am unsure how much this project will cost as I have no experience in this field.