.....loading up on neoprene, with multiple thick layers, will make you float like a cork, necessitating a possible massive amount of lead to sink it, which will be a pain to deal with, especially depending on the exact dive procedures/methods you will be following......trying to walk around a heaving, slippery boat deck, or getting into or out of a zodiac, with lots of lead, will not be fun! Also, massive amounts of neoprene make bouyancy control, especially at shallow depths, much more challenging, even more challenging if the water is already rough/turbulent. Also, I'd choose a one-piece thicker wetsuit over a multipiece thinner 'layered' wetsuit any day of the week.....'layers' provide too many water entry points. As already suggested, Galapagos isn't the place to figure out your bouyancy, get in a pool at least with whatever configuration you will be using on location (including the same tanks as the boat will have) and try to dial things in as closely as possible. (making the obviouss adjustments for fresh versus salt water.) Warm gloves and thermal head protection are critical as enormous amounts of body head are lost through the head/neck areas. AKONA makes some very nicely designed gloves with armored fabric, they're tough and have the best wrist sealing design I've yet seen in a wetsuit glove.
As already mentioned, if you go with 'semi-dry', I'd HIGHLY suggest you try that out at your local dive shop BEFORE dragging it all the way to the Galapagos and THEN discovering you hate it! They can be a bear to don/doff, and it's easy to overheat in one if there is a time interval between zipping up and splashdown...again, IMHO, Galapagos isn't the best place to experiment with substantial amounts of major new gear.