Would it be possible to add a setting for the max productivity research level?

Why?
Allows limit the max level so that max productivity needs a combination of research + modules + inherent bonus to be reached.

Would be nice to have an option where it stops at 300% productivity like the normal game - better yet update all the productivity techs so once they're useless you can no longer update them.

The techs in this mod already stop at 300%.
Will consider adding a setting to define a lower cap, as well as one making them all infinite - probably this weekend.