My friend and I have played with this house rule a few times, and it’s worked well for us so far:
Atomic Bomb: Must designate research goal before rolling research dice, paying 20 IPCs for 4 dice, must get 3 breakthroughs (odds of 20/1296) to achieve goal, limit of 1 such research attempt per turn. Atomic bombs cost 20 IPCs to build, must be built in a Major Industrial Complex, are carried 1/strategic bomber, and kill primary targets (3) at 5, secondary (4) at 4, and tertiary (8) at 2. Primary targets are announced beforehand by the attacker; secondary and tertiary targets are chosen conventionally.
Hydrogen Bomb: A result of 4 breakthroughs (odds of 1/1296) unlocks the Hydrogen Bomb, 25 IPCs, allows for the naming of 2 ground zero casualties before other casualties, and increases the number of tertiary targets by 3. Facilities are completely damaged as primary targets, half as secondary, third as tertiary, and taken off the map if named as ground zero targets of a hydrogen bomb attack (ICs can’t be ground zero).