After reading the thread on Dead Planets I noticed many who like the idea of simply destroying entire species and using burn all policy. I think we should have this in game but tie it to things like diplomacy.
For starters, Planet killers or whatever you call it or such are not enabled by default for the AI, the player has to do it first. Once that choice is made the Player suffers awful diplomo penalties for such an act (see Babylon 5). Also a check should be made on population happiness which in turn should also tie into a bonus or penalty to production.
Then the AI would be enabled to do it to you. Depending on tech level if word gets out of your genocidal deeds you will likely be the target as well of such awful destruction.
If you want to simply glass a planet by all means let the rocks fall! But there would be a terrible cost to start such an event.
Anyway, I know we are in Alpha and this can be a mod for later days. I just thought I would toss it out there and see what you all think.