I think this is likely. I suspect it will be a team of people on call with each team monitoring a 3-5 autonomous ships. Honestly I feel like the bridge could have been mostly automated since the 1990s and fully automated by the 2010s but the regulators deciding on if humans were needed were always ex-captains of various flag states. Think how many maritime accidents have been caused by human error…
Engine side of things will be challenging, but if you make the design using a duct keel as a heat sink it could probably be done today. Keeping salt water out of the engine room is a hard sell for a design since its such a cheap and readily accessible way to cool things but it would be very much needed for this. Then as long as you use wound spiral style gaskets on everything it would just need a scheduled maintenance period where essentially you remove everything in the ER and replace with new while the old stuff gets rebuilt. Just keep a few tanks for filling up various fluids/oil up top on deck and occasionally refill/ and pump ashore minimal bilge leakage.
If you want to rebuild equipment on the ship it’ll be out of commission too long unless it is a shipyard. Plus it’d be a real loss of the benefit of going autonomous… either conditions on board are made to be livable or they aren’t… if you bring crews onto the ship you still need lighting, stairwells, ventilation and don’t forget the tools and space needed to do rebuilds (and you’ll need a large workshop, and working area around the equipment if you want to bring a crew large enough to rebuild a lot of equipment all at once… cranes/lifting gear and so on. Then the ships looses a major benefit of having a crew and that is continual maintenance while running. You’d also have all these tools/equipment to maintain the ship that are only getting used during a major service.
Just make the engine space a series of cartridges that you insert and weld in as a block. No wasted space, no worries about livability, no extra wiring for useless aux electrical systems… Just design it well enough to last 5-10 years and then cut it out and weld in a new block. Design the hookups to be flanged and wire connections at the cut points and it could be done fairly easily.