At this point (but note the idea below), I think I would ***not*** want the AI team to implement support for this, because I think if an AI went on a planet-destroying rampage it would make for an un-fun game and really piss people off. I question the whole idea of making more planet/system destruction content, but it seems especially poor for the AI.Pretty much done, tested and should be working, except I haven't taught the AI to utilize this. If someone from the AI team would take this on, that'd be great.
Design-wise: DeathStar capability that only requires surviving a single round of combat seems over-powered to me. If we want such a thing at all I think it would need to be astronomically expensive, ***at least*** an order of magnitude more expensive than now, perhaps two orders of magnitude. Mostly, though, I think it should require a longer period of time, by working with specials that get applied to the planet, advancing them along a sequence of at least like 4 or five specials before destruction occurs (and if the deathstar ship is destroyed or leaves the system then the specials cycle back down one per turn or just totally disappear right away). And even then I think it should be much more expensive than the current cost.
Overall, though, even with the changes I propose above, I am doubtful of this being good to add to default content. Perhaps have a new Rule "Allow Planet-Destroying-Attack Content", defaulting to False/No, which would gate availability of this ship part (and perhaps Nova Bomb also, or perhaps generalize to include things like Gateway to the Void). Then gated by such a rule I could see the AI being enabled to use this part, there being some chance that a maniacal AI might choose to go on a planet destruction rampage.