Please no. Something faster than a cyclops. I enjoyed cyclops being a mobile base, but my god was it slow. I don't remember what issues I had with the sea truck but I'd probably still prefer the truck to the cyclops.
You know what my thing is? The Cyclops is huge, and most of what you need it for is exploring a cave network. It would make more gameplay sense if you got a big boat or submarine that acts as a base of operations, and then something a little bit like the Seamoth for deep submergence.