Just so you are aware, in one of the other suggestions, there was a request added to their list was to put technology limits (ie, medieval, moderns, etc.) on a per world basis. I think this will address your desire for restrictions to only low tech, Geneo.
Signed up for the forum just to say I love this idea. Haven't played the game yet, but from the vids I've seen etc.. this idea would be great for this game.