At that point you're making it more an across-the-board "badass" variant as a "sabertoothed" variant (which is by its nature quite badass)
This mod seems like an awesome project, but I'd think its going to be hell to come up with good variant types. I'm assuming at this point the sabertooth and dire variants will end up being combined to form some extra-badass but not giant variant.
Also, one thing that can make creatures' attacks stronger to a degree without changing too much else is upping the thickness of muscle tissues in relation to others. Not sure if that's even possible through the creature variation framework, though. If it isn't you'd have to write in the changes through the individual creature's definition.
If you're willing to go through that extra work, I might suggest a "supernatural" variant, which gives the creature the supernatural tag (removing the natural and mundane tags), and giving the creature one or more sphere tokens (say, giving supernatural cows the agriculture sphere). Toady intends, at some point in the distant future, for biomes relating to spheres to replace good and evil biomes, and this definition may or may notnfit right in whenever that update comes.
Also, the spheres a creature has govern what interactions it innately knows, if those secrets come with the supernatural_learning_possible token. In a world with more than just death secrets, there could be many magical deer. Or dingoes.