Research Tree Tweak - earlier anti-alien gas

[beng]

In 2.5 by the time the anti-alien gas becomes researchable, I have usually finished all the research requiring live aliens so there is no longer any need to stun them or take them alive. Either there should be more research requiring live aliens, or the stun gas should be earlier in the research tree.

[anonymissimus]

I'd rather consider gas grenades an upgrade for fire grenades, as the ladder do very little damage against the medium alien armor.