THe problem here is that there is litle inf on the Shivans.
They are Xenocidal, they are cybernetic, maybe even engineered.
But, how did the Sathie fleet tied in with the lucis?
was a lucy Fleet that did the ancients? the whole thng with the shields seems to be, specially since the lucy's shields were qualitatively different from the fighter based versions.
actually, the big question is, do shivans adapt? if the differences between FS1 and FS2 are because they realized how vulnerable could the lucys e... their industrial capability is nothing short of monstrous.
of course, maybe the lucy flets are rovering bands that go for decapitation strikes against other sentients and the sathys and co are tasked with other functions. and we can't even beguin guessing why they decided to turn Capella nova.
Though, I do have an idea about that. we know, more or less, that shivans are not planetbound (at least the ancients seemed to think so) what if cooking off Capella was their way of "Shivaforming"? remember the Nebula? thousands of years old, those were bosch words (sure he gave a higer upper limit, but also mentioned the thing in a what if it was witnessed by the Pharaos...
(course, if that's the case, those knossos portals are tough as nails)
As a counterpoint, yeah, the mission beyond the nebula was beyond the nebula. so maybe not, or only certain stars could go though the process... who knows. maybe they are making galactic art and are very sensitive to critics...