Don't know about modding, but what country are you playing as that's having manpower problems? Might have a few tips. I know I was bleeding manpower and always short before I figured out ways to conserve it that were not at all obvious or intuitive, lol.

Its not a problem of manpower. I always have too much and I began destroying all my training camps.

Finished a game and I have so much manpower that i makes no sense.