The Yama is an awesome looking ship, but it's actually part of INF private assets. The Kismat (don't know if you use it already) is quite similar looking. In case you want to replace it later once the Yama is available, you could use it as template. I think there's a decent number of hi-poly Shivan destroyers available now (compare with the situation a year ago), you don't need to spam different classes of shivan destroyers (there're only 3 in canon if you include the Lucifer). Or does the mod play at several differnt time points?
In Blue Planet, there are at least two types of Shivan destroyers: line destroyers and strike destroyers. The Demon and Ravana are classified as line and strike destroyer. In this mod, there are many types of destroyers, like multi-purpose destroyers, missile destroyers, fighterbay-less destroyers, heavy destroyers and so much more.
The Kismat I used is probably a line/strike destroyer hybrid, so I do not plan on replacing it (though I plan to hi-poly remake it) nor using it as a template. As Rampage said, the Yama is an Inferno exclusive, and thus is currently part of INF private assets. I think it comes down to tech room descriptions.
The mod plays at several different time points, since it is set about 3,000 years from now because it's in our future. It may overlap with or set after the 2018 Mortal Engines film adaptation of the 2001 novel of the same name by Philip Reeve and any sequels.
EDIT: Let me remind you that Shattered Stars is a logical epilogue to the FreeSpace saga following Blue Planet. It's about the Shivans, and they have been driven by revenge after being banished from the Great Council formed by Brahma in the First Time by Vishnu and the Vishnans from Blue Planet. They encounter living weapons of destruction and at least two new alien species, all of which appear to be one of the caretakers of the Vishnans and the Brahman civilization. They wage war against each other, and the new Great War begins.