Nah, you could just have a fire particle that plays and slowly dies when the planet is hit by bombardment. I think that would be more likely in a mod than a DLC though.
Its not the same, i would give you benefit of doubt, that its perhaps doable, but as of now i think what i have in mind is possible to do only by texture. Preferably animated one, where the intensity of surface "burning" is varied.
On topic of more DLCs, i agree with your opinion, that they probably dont have much influence on potential development of Sins 2. And yeah, i still want more DLCs.
BTW, i dont know who exactly was responsible for each of the Sins game, if the first one was purely Ironclad game published by Stardock, or it was some kind of joint venture between both companies - mostly from the game-design standpoint. The same goes for Rebellion. Bottom line, i like the Rebellion the most of the series, for me its the ultimate game, superior to the original in every possible way, so i hope the same people, regardless of the company, are going to work on Sins2. Especially the ones, who came with idea of subfactions and Titans.