In outside levels there are ways to blur the edge of the world towards the horizon with some clever and skilled artwork and level design. However as TGC themselves point out and are aware of the current world size limitations and that the edge drop off point of the world is not condusive to giving even the appearance of reasonably large levels especially when viewed towards the horizon from high vantage points.
You can do the best you can but in all truth the FPSC world size relative to outdoor areas is small and thats an end of it.
The simplest solution for TGC would be to extend the world size to include a capability to include a terrain or other world objects outwards towards the horizon line even if gameplay area was to be restricted to the current world size.
I hope they might consider that but it would presumably depend upon a level of increased engine efficiency and we have no idea currently if that might be possible.
Personally as everyone knows I am for no imposed restrictions at all so that such things are left to the game designer to decide in the gamemaking process as appropriate. That is not however TGC opinion as far as I am aware.
"I am and forever will be your friend"