The short answer is yes. In fact I vaguely remember someone doing something like this.
You can create your own maps using the basic system. You can also add your own characters and weapons, however I'm not a modeller,so best ask around.
You shouldn't need to learn a new langauge, but I'd advise taking some time out to look at the FPI scripting.
The best guide for syntax is
here
You should also find alongside the manual in the Docs folder the latest version of the community guide, which contains many pages of great advice.
I hope that helps.
SC