Quote from SomethingSlimy
What if gas instead acted like water, only upside down? It would flow upward, and you would loose air bubbles when in it. Perhaps source blocks of gas could be collected with empty water bottles? One problem with this system though, would be that gas source blocks would be infinite, so if gas reached the surface it would create an unappealing streak into the sky. Perhaps gas could have a finite system, instead of source blocks. There are mods that do with water, but I'm not sure if it would be a hassle on the performance.
I actually really like the sound of that. Perhaps instead of having the gas ascend infinitely, it would stop after reaching a certain height so that it would be limited in quantity and wouldn't create streaks in the sky. The idea of being able to collect the gas sounds interesting, but of course, it would need to have a purpose. Being able to make a hot air balloon with gas would be cool.