I've heard this has been asked, but not sure if it's been posted here, but a captain should be able to change the size of their ship with out requiring them to leave the lobby and start anew. A very easy way to include this would be to use the code from the scuttle system.
Essentially you off load whatever you supplies you want for the new boat, you go into the menu and vote to change the boat size, obviously the boat sizes available will be dependent on what the current team size is, so to get that sloop, two crew members will need to leave. You select your new size of boat, and it scuttles your current boat, then upon respawn, instead of the old ship, it's the new one. Then you just put your supplies in the boat like normal and sail on.
