Heh, if you're any good at coding I would personally try messing around with the Q3A source. You will however need a C++ compiler, but it is far more powerful than FPI scripting. You will also need modelling tools, of which GMAX and ms3d work excellently.
Lastly, you also need a mapping tool. This works slightly differently from FPSC as you carve your level out of blocks, but it saves the ridiculous process of having to create a whole new segment for a flat wall.
GTKradiant:
http://www.qeradiant.com/cgi-bin/trac.cgi
IOquake, an improved and repackaged Q3A source:
http://ioquake3.org/
Interestingly, you may be able to use GTK to make FPSC maps, as I know you could do this with darkbasic.