I would like to see Leviathan pop up here (if only to give me a reason to play it more xD)
Though I can see why it may not have been added, having a lot to do with luck an' all. That said, plenty of other games that are randomised are speedrun, so I don't see why we can't give it a try! If the mods add it, I'll happily attempt some runs.
ETA: Definitely curious about how song choice might work (after reading James' reply here). Would we have to use one song only? Would we have to use three specific songs? Is it player's choice? There's a lot of ways to work a Leviathan category!
I'd love to see Leviathan added as a category. Would probably need a rule standardizing the soundtrack (I mean, using Nihil's song only out of base game tracks would be fastest in theory), and it comes with an In Game Timer showing you completion time for your run, so it could work pretty well I think.