Sorry, but I really have a hard time believing this. I mean, it isn't like this is the first Fallout 2 mod, and I've heard nothing similar from other Fo2 modders. Also I can't really understand why it is a problem to do this with the Fo2 engine, but not with the FOnline engine. If at all, then the FOnline engine by definition would be a problem for them.
Regarding the other FOnline stuff: Most should be possible to be done in AngelScript, without touching the engine source code. But I personally am not a programmer, I know nothing about the details.