I don't mean to thread jack, but when I first read "Doomed Planet," I thought you were suggesting perhaps a planet that was on a timer. In terms of role play, it could be that the sun in the solar system is going supernova. Or maybe the planet's own core was expanding to the point of explosion. Either way, what if there were planets you could scan that had very high resources, but only a short time you could occupy/ control time? The planet would disintegrate after a month. The timer would be visible to you, but not to any attackers (as they would not have been familiar with the solar system or the planet's true condition until conquring it)

2-3 mega resources across the board.

But wouldn’t that mean u don’t realise it is doomed till you colonise it? (From uninhabited status) or dose its apocalyptic countdown begin upon colonisation?

I like the idea but think this would be heaps cool as an NPC reward/drop.

Actually, I like your take on it too. Perhaps the planets have a range of life span from 2 weeks to 1 month. And, you don't know the condition until you claim it and the count down begins.