Mutated dinosaurs can give a nice touch in terms of gameplay, adding a bunch of different enemies.
Here's some examples:
-Brutalis Nova: Is way dangerous and has more HP (mini Alpha Raptor), it can pounce.
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troodon mutation for nova: is way faster, and a bit more tiny.
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Dilo mutation for cerato: can give poisonous damage and spit venom
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Adult Dilo: bigger and has almost bruisers HP
And more...you can really go crazy whit it, there's a lot of variants you can make for each dinosaurs..
And in terms of lore it could accentuate the absurdity behind the Phoenix experiments and the damage they caused.