The better way to fix that lifesupport issue is to include a second lifesupport component on your ships
Then you can leave the little destroyers and stuff only needing one. (Make sure the appropriate settings are in the purchaseships.txt files)
Adjust "Base Crew death rate" if need be. With the lifesupport providing 1 one ability point, you need the amount specified in BCDR to keep 'em alive.