I'm not sure why you seem to think script development is entirely distinct from software development. Perhaps you have some insight into this that I don't, but while there are some obvious differences, I'm willing to bet that a good IDE that's general purpose enough to work for both a lisp and static language and support refactoring and syntax highlighting and interface with external programs like source control would support quite a bit of what's needed already.

As for implementation language, I'm not sure java is significantly slower in the case of the project size we are talking about here.

I know scripts rely heavily on centering and right alignment. I'm guessing that's not the only way they depend on the assumption of being printed. There would be some impedance mismatch in using tools designd for plain text.

You could write in Fountain syntax http://fountain.io/ and have the presentation be printed as intended. I actually tried that once or twice (short commercial form) in Vim and I didn't have any issues.