Funny how new game creation programs pops up and questions about fps engines after I announced Easy FPS...
Quote: "you would probly need dark basic pro to do that, (just check out FPSC)"
No, not at all.
Quote: "Say I was making a FPS game engine in DarkBasic and I needed to build an executable from the user's map. How would I do this?
"
See, you don't actually build the exe. You simply have a pre-compiled exe with your engine. When the user make and save a level you could make a build game function that would copy all media the user have used in his/her game to the users project folder, with the exe. When the user runs the exe, the exe will read the level data and build the game from it

Simple as that. That's how I do it.
And just admit it. You are working on an fps engine
-The Nerd