What about updating the mod to Factorio 2.0 and Space Age?
Instead of adding new versions of the furnace, just introduce module slots. More research to add more slots.
Increase the initial cost of the nuclear furnace to balance its power.
Add sound effects for better immersion. By the way, you can use the processed sound of a nuclear reactor.
Consider replacing the sprite (the original one is good, but a fresh look wouldn't hurt).
