I feed all of mine in their enclosure - on any kind of bedding, used to be aspen. I've fed ball pythons at NERD on cypress bedding. There is no one in the wild making sure that snakes aren't consuming leaf litter and twigs. They are perfectly adapted for ingesting small amounts of substrate with no negative effects.
While I've heard the warnings of impaction, I've never personally heard of anyone report that their ball python became impacted from ingesting substrate.
Their stomach's break down bones, toenails, teeth, fur - a little bit of substrate will also be broken down as well.
I'm the opposite of you though, I don't have freezer space to keep a bunch of frozen, so I've always fed live. Never had any significant issue with it, and I've fed off over 4000 prey items since I've been keeping ball pythons.