That just means that we'll have rulers naturally selected based on their access to valuable resources and labor for which others are willing to pay highly.

The fact that the bodies are chosen by the people they represent (like a labour union) they can be replaced as soon as they are seen to be doing something their constituents don't like. (Instead of having to wait up to four years as is the case in the current system.

As for the self policing idea, since the representatives are not anything more than simply representatives, should they decide that only the purples had to work, the purples could have that person replaced immediately since there's no need to wait for an election.

Of course the elderly and sick etc wouldn't have to work, 0% unemployment doesn't mean that, it means that everybody who can work, does. With a welfare system to care for those who are more vulnerable and an education system that actually teaches children things that can help them contribute to society.

If group X wants something that group Y prooduces but group Y wants nothing group X produces then group Z can get involved in a trade. Similar to how multi-team trades work in baseball. X wants timber which is produced by Y. Y wants grain which is produced by Z. Z wants fruit which is produceed by X. X sends fruit to Z in exchange for grain which it then trades with Y for timber.