Nav Sublayers

I was a bit disappointed to read that sublayers in the Nav are not yet supported. I love the ability to add products and have drop down lists for product specificity but I feel the lack of organization right there in the menu might junk up my users online experience as there will be hundreds of products on the site. Does anyone know if adding a CSS navigation menu created by a CSS menu maker will work? Can the code be successfully implemented into Squarespace in lieu of the built in one?

Many great attributes to Squarespace but I find this one troubling for me. It may not be a deal breaker if I can find a work around or somehow creatively organize the products.