The old system with the jail cells is a good idea, seen it done on other servers and is always good for a laugh but a part of me would miss the island because its very well done, so why not have both?
Lets look at it this way... you're jailed for fighting on the ship. So, if someone fights they are sent to the jail cells for 2 minutes.. crowded jail cells, however the same rule and script thats on the ship applys in jail...no fighting!
People in jail get, for a example, 5 warnings about fighting in a fight free zone and if they do, they get sent outcasted to the island for 3 minutes! (this will also stop them hitting people through the bars when people visiting are standing up against the bars pissing on them)
Jail is all about rehabilitation afterall, and making prisioners control themselves not to hit people who may be mocking and dancing at them in the cells will help them learn control.
Oh, a chainsaw weapon spawn is needed at the /visit spawn too