okay one. the game is going to be released in 10 days so they wouldn't just "boop" here have a giant sub. also the games terrain makes it so something like the cyclops would be too big to be able to go through most biomes the only ones it could really go through being the tree spires, the lily pad isles and the arctic. (not including the void). so i would say no. no there will not be a cyclops replacement. the seatruck to made to be a mini cyclops as you can add a bunch of cars to it. so as
@Kindadumblol2 said. it is really the replacement. the only REAL differences between them are as follows.
1. it is also made to be the seamoth replacement so without any cars it can go as fast as it.
2.it has less health and can be repaired from everywhere. the cars themselves have their own heath though so being hit in the back does not damage the cabin which does lead to one of my personal gripes which is the fact at how slow it repairs to be the seamoth replacement. it takes the same damage too.
3. obviously. size
4. you cant use the builder tool inside. the functions of the things you would likely place inside being taken up by the different cars you can use.
5. the upgrades