We have webber and spider befriending for Reign of Giants, and we have Wilbur and monkey befriending for Shipwrecked, I think a fun plant character could be entertaining.
He'd naturally befriend the plants, and everyone else would be hostile to him. He wouldn't come with too much fancy abilities, being more just a way to live in the rainforest without being murdered by the snap plants (you'd still have to watch out for the vine-tentacles, spider-monkeys, and insect fellows). Perhaps he gets less sanity penalty from rain (he is a plant after all)
just a thought =P i really like the snapteeth plants, and i love the rainforest