Now, does anyone have any input as to whether this should be a terrarrium or vivarium/ paludarium? I want it to be 50/50 water but not if that poses a risk to the gecko / anoles / skink. Thoughts?
From what I've read, Crocodile Skinks readily swim. Can't verify that, though (it's just "information" I've picked up from various care sheets, I'd recommend asking a breeder/keeper about that). And I know Anoles can, not sure about the gecko.
But I would imagine as long as you had the water not too deep and with easy access to get in and out, that it shouldn't be a problem on that side. I'd be more concerned about getting proper filtration in it, but there's a bunch of really great set-ups by ZooMed and Exo-Terra now that are specifically designed for people who want 1/4 - 1/2 water in their enclosures and have a pretty decent filtration system in them. My friend uses some of them for his tropical frogs and Caiman Lizard (different enclosures).
Not the biggest contribution, sorry, I'm sure you'll get more solid answers from the others, lol.