While I'm basically okay with the thrusters being exposed on the ROV, I think it's probably better for my own fingers if I put some kind of protection between the whirling propellers and me. So I had Tap Plastics cut me 12 pieces of 3.5" long, 2.5" ID, acrylic tubing which fits around the thrusters, with a little room to spare. I made mounting holes in the tubes using a laser cutter. The results can be seen below:

Not sure how this will effect the thruster efficiency; either positively or negatively.