[Suicide Junkie]

While still remaining compatible with stock, it will be difficult.

You would probably have to use somewhat more of a trial and gradual refinement system with heavy use of the map analyser.

What you might do is to add some more none-atmosphere planets & moons.
Then decrease the number of atmosphered rock/ice planets to compensate.
You would be trying to keep the total benefits for breathing rock/ice races the same while adding to the vaccuum breather stats.

In any event, gas giant races will be unique from rock/ice breathers, and also unique from vaccuum breathers.
The trick is then to make those three classes of race all be fairly balanced between each other.