"I think there may be a 'window of opportunity' during which bronze foxtrot is a usefull tool for teaching concepts like a good walking action and posture."

I don't think of Bronze Foxtrot only as a tool for teaching concepts. I think of it more as a useful Dance to know, almost separate from higher level Foxtrot. When dancing in social situations where most dancers do not know LOD, let alone the Silver or Gold Foxtrot, it lends itself well to dancing amicably with a partner and the other dancers.

I live in a rural area where the social dancers predominantly dance Bronze level or a stationary cuddle. The dance floors are usually in Community Centers so they aren't large and trying to dance continuity in those situations is almost impossible. If you are going to dance it will be Bronze level.
I travel to nearby cities (1-2 hrs away)with larger venues to dance continuity.

If you are dancing only at venues where the majority of people are dancing Silver and above, then it will probably be seen as that "cute little dance". But as Jonathan has already mentioned, inserting Bronze figures into your higher level figues can make it interesting.