man, the level of support with this project is really unheard of in my experience in the past open source oriented projects; what great developers we have here.
Being a programmer myself albeit not a web developer I see your concern with the problems, and I purpose we simply Loop the main Theme display code.
Current theme display goes like this on the front page
MAIN(which really isn't a category at all, let's name it 0 and call it the index) so the index is 0, so it'll display categories [1], and [2], and [2] being the sub-category of [1].
Now let's suppose the user clicks on a category on the 1 index. it'll load a new page that's similar to the front page, with the except now the index is incremented/changed to [1].
so it'll load categories [2], and possibly [3] if it exists, much like the current front page code, and if users click on [3] it can go further, and load more categories, much like the breadcrumb plug-in intended.
Now I have not looked at how osclass is designed so I'm not sure how hard this is to implant, but it's an idea.
Let me know!
and Thanks again for all your hardwork.