You should include things like
the old visitor center (including the lab)
a rideable jeep for transportation (like the origins tank. If that doesn't work, you should make it work like a zip line) downed fences with generators as electrical traps
Rescuing NPC's that help you
Have a round with flying dinosaurs (quetzalcoatlus, pteranodon, etc.)
Buyable ending with calling in an airstrike (suppose the team was sent to destroy the inhabitants as they are a threat to the rest of the world) and having to run across the map to a boat or plane in time (like linking a teleporter)
Collecting samples from different nests and taking them to a drop zone to exchange for points (say the team is also there to collect samples for Ingen)
the cutscene before the game starts should be the briefing for the mission to the island.
A sort of special grenade that works like a vial of pheromones (like the t-Rex urine mentioned in Jurassic Park 3) that calls in a dinosaur to fight the zombies, or yourself if it sees you.
A special grenade that gives you a team of trained Procompsognathus (commonly referred to as Compies) that work like the hell's retriever. They run and pick up drops, jump on and damage zombies, and come back. This could also be used as part of an Easter egg step, were you send them out of the map to grab something
Most off all, don't just make this a themed map, make this a full blown story with as many features and entertainment as possible. Make this as intricate and fun as the Leviathan map.