Drag and Drop Divider Bars
I would love to have newly added podcasts not create their own categories and to be able to display and sort all of my custom categories on the main screen at the same time. However, if overhauling the category system is too drastic, then maybe you could just add in custom divider bars that could be used to sort podcasts on the main screen through drag and drop when "custom order" is selected for sort. It could be a totally manual thing without having to complicate the sort or category features. Just dragable bars with custom text to allow for visual sorting of podcasts all on one screen.