Perhaps this has already been considered and dismissed, but I feel like it would make perfect sense for the Black Hole Talisman to be able to draw blocks from the Rod of the Depths/Lands/Highlands.
My motivation for this is the following: The Rod of the Shifting Crust already can draw infinite blocks from those rods, and it can also draw blocks from the BHT directly, so why not "close the loop", so to speak, and let the player draw infinite blocks from the BHT directly? It would be very convenient for crafting purposes to be able to draw a stack of cobblestone straight from a BHT rather than mining it/making a cobble farm/getting pebbles (GoG).
I could have sworn this was already a feature but after rereading the Lexica section about the BHT it seems that I was mistaken and had confused it with the Rod of the Shifting Crust.
I'm not dead-set on this feature or anything, I was just really surprised it didn't exist with how many other synergies between trinkets there are. Maybe there is a technical reason for it?