The shuttle wingspan is 78 feet, and the narrowest section of the Intracoastal Waterway is >100 feet. You simply wouldn’t have to disassemble the shuttle to make it work.

There are existing rules for wide loads. They’d just use them.

That’s the extent of my knowledge. I think that everyone they’ve talked to doesn’t want it to happen, and that is coloring their view of whether it can happen. But I could be wrong.