Just completed a run of Subnautica in which I never built the Cyclops. It turned out to be easy until it was impossible.
There are three purposes for which I've driven the Cyclops around. Carrying the stuff for a new base, bringing vehicles to the Tree Cove (I like to build a base there), and carrying the Prawn into the lava zones.
Eliminating the first was mildly challenging. I cleared my inventory and carried starter supplies to get new bases built, then built them out using mostly local materials. I typically had to make a second trip for the seeds, but could have done without that. Most of the running back was just for stuff I'd forgotten, which wasn't the fault of having no Cyclops.
The second was tricky, but I found that three well-placed Exterior Growbeds full of Brain Coral were enough to get me from the Tree Cove to the top of the Blood Kelp Trench via Seaglide, and I had a base there already. So I could just make two trips for my two vehicles, and it also made the Lost River generally easier to explore.
As for the lava zones, the Thermal Reactor and Jump Jets made traversing them by Prawn alone much easier than trying to lumber around in the Cyclops. I slipped right between all the Lava Larvae and walked under the Sea Dragon's nose.
Unfortunately, after pretty much beating the game without ever building the Cyclops, I had to build one anyway just to fabricate the shield generator for the Neptune. Ah well. Maybe I should have put a spare in the Time Capsule.