This is a really cool idea! Would definitely make the cube of meat more unique aside from just being a Wall-Nut. Also I agree that Bum-bo tracks go hard asf.
Maybe a Lil' Brimstone baby that works similar to coconut cannon from PVZ2? It could cost around 350-400 and charges up a brimstone shot you can fire on command with a click?
I had an idea for a special D6 mechanic: When the D6 is used to re-roll, it becomes a cracked die and can re-roll again at the cost of losing the D6 for the rest of the run. The cracked die will recharge into the D6 after using it only once though.