The only moderately expandable game creation system by TGC is FPSC. X-Quad is not even by TGC, but really what it is, is a map handling system, designed to let you make maps then run around them. The idea is that you rough out your game idea then expand on it in DBPro.
There is always Leadwerks 2 - which is a bit like the FarCry editor, but with a full game engine behind it. You could use scripts, although I'm not sure what these scripts can do, but there's also the possibility of taking the game further by using the engine alongside C++. Perhaps looking into the script system would be an idea, it might be capable of doing all the you need of it.