Geometry for sure is the key.

I like a basket in front for throwing stuff into, but not for heavy loads.

I like the heavy stuff in lowriders in front. I like the front basket to be as low as possible. My 20" folder has got low frontbasket plus lowriders. I put most of the weight in the front when touring with it plus a traier if needed.

Sounds like you need a longtail. I am building a 20" longtail just now. Good since it is shorter than other longtails andcarrying the weight lower.