Items that affect both heat and energy. Sheilds that spread the damage between increasing heat and reducing energy, not shutting down until both have reached their limits (when heat reaches it's limits it'd move entirely to energy and vice versa). There would also be guns which both increase heat and drain energy. I understand that these would be hard items to get, but they are a gap in the game, especially the sheilds, as using many turns rearming sheilds can be infuriating, another option would be sheilds in their own right- not converting energy or heat, just reducing the blow with it's own health, regenerating over time.