That's an interesting idea I hadn't thought of. So basically each player gets a default list of presets when they first use /mycar. They can customize the presets after that as much as they want and make new ones. Then, if they want, they can also reset their preset list to the current list of default presets and start over. That should be possible, and it could be a separate feature from the common presets idea as well.
I already did most of the work last night to implement common presets. I will spend some time tonight testing it and probably make a release. Here's what it looks like currently:
Players with permission to
use common presets can do:
mycar common listmycar common <name>mycar common load <name> (also requires the load permission)
Players with permission to
manage common presets can do:
mycar common save <name>mycar common update <name>mycar common rename <name> <new name>mycar common delete <name>
Once the player spawns a car from a common preset, if they have the permission to use personal presets, then they can save that car as their own preset if desired. It should be possible to allow players to use common presets only, without allowing them to have personal presets. The player would still require the spawn.2-4 permissions to do this, so the plugin can determine which preset length they are allowed to have, meaning there still won't be a way to prevent players from spawning random cars (not sure why anyone would want that but someone asked for it).