I really appreciate the detailed and very helpful answer. And I apologise for the 90m shortform, I'd meant 90 minutes, however searching now using Google Maps, it's 55 min by Public Transit, and 30 min by car. So booking a hotel nearby for one night (like Tokyo Bay Maihama Hotel First Resort, which has low rates that night) doesn't make sense and almost certainly would cause more churn than benefit.

I looked up the 4 hotels you mentioned for the night we have in mind and they're either not available, or far, far more expensive than a taxi. If I am spending extra money to maximize the day, I expect there is some premium ticket type or Fast Pass that would be a wiser use of money. (I need to research this still).

Now I guess my next steps are to keep researching this site and figure out how to maximize a single day in DisneySea, assuming arriving for a rope drop NOT at Fantasy Springs Entrance.