Good news and bad news. First, the bad news. At this time there isn't an easy way to add or remove options fields. This ability is in the works, but I don't have a solid time frame on when it will be available.
The Good News, there is a side project being developed to turn Car Demon into a PlugIn for Boat Sales. I'm not one of the developers currently working on the project, but I have seen a beta version and it's moving in the right direction. Essentially it is installed along with Car Demon and the changes all references to Car to Boat and has an option list for specific to boats. I've sent an email to the developer working on it and asked him to please find the time to swing by here and share some more information on his project as soon as he can.