I've done some searching and haven't found any. Not even a mod that affects the unit cap.

AFAIK no.

There's a total modification of the original Perimeter called Perimeter: Initiation. Sadly it appears it's still in development and there's no indication if it's ever going to be released or not. Also, no English version of the site, so you'll have to use a translation service: http://exodist.net/diaries/.