In the 'Hello My Name Is Ice Cream' book by Dana Cree, she provides a game-changing suggestion to boil a bit of pastry in an ice cream base, which flavors the base a bit, and provides gelatinized starch which stabilizes the ice cream base.
So I've done that with a couple different things, to varying success, and thought to myself, it should work well with gravy. So I tried it.
What I did was, added seasoned stuffing mix to chicken broth, and boiled it all together, and hit it with an immersion blender when it boiled. The gravy thickened up pretty well, and I strained it to get rid of any lumps of bread that were left.
I didn't like it. It didn't taste right, it was too seasoned to be gravy.
I guess if you want you can try just boiling dehydrated bread in chicken broth, and season it appropriately. I would consider trying to add a bit of butter, too, because gravy should have some fat to it, and theoretically the starches gelatinizing will help emulsify the fat into the broth. I don't know. Maybe I'll try it.