I've done both of these things on my new quarry setup and it's looking good. I actually forgot to place the second water block for my Aqueous Accumulator before I encased the engines in obsidian, and one of them blew up after a couple of minutes lol...good test though. It only knocked out the engines, the quarry, and a couple of pieces of pipe. All of my chests/barrels were intact so that was great. I'm going to stick with this setup; although I do need to break the casing to refuel the engines at about 2/3 of the way through, a few blocks of obsidian is no big deal.