Its not only about the Lightning. I want something BIGGER i mean the source engine is really limited what it can run on map sizes and i have never seen a really "open world like" map for such a thing.
I "maybe" found a Programmer for it i will do some of the mapping. (Programmer is still thinking about it) Also most likely it will just take the art style like robmaister said without the hl2 content but a similar storyline. Still searching for help if anyone wants to ^^
Don't be stupid, make it as a sourcemod.
Lighting can be optimized with that, effects can be added in the shape of shaders and there are already a ton of brilliant maps out there. Work effort -80%