I have never been so hyped about anything before...really..
can´t wait for more Informations, i think this should be really possible to balance. The Humans would need a kind of head Start, or the Dinos could just work together and crush them inside their Thatch and Wood Bases.
Later on it should be kind of even i guess, the Humans got Weapons, tamed Dinos.. vs. "wild-Stats" Dinos (which could work together to defeat a Tribe).
But it should have limitations of some sort, like even if all "Dino-Players" start with LvL 1 there should be like only 1-2 Gigas, Brontos, Rexes etc...(for Players to choose from)
I also think it should really hurt as a "Dino-Player" to be killed, like if you loose your Base as a Human.
I could think of this like: i choose a Giga, playing for weeks, getting killed -> then i cannot play as a Giga again for a period of time. So you would prevent "Giga spamming" upon the "Humans". And other "Dino-Players" will have the Option to take the Giga.