Not only could you do that in Postgres, but you could do it in a real language of your choice. The reason you don't see it done is because the people who choose

Not only could you do that in Postgres, but you could do it in a real language of your choice. The reason you don't see it done is because the people who choose Postgres over Oracle know that it's kind of a terrible way to build it if you care about long term maintainability. That method of building fossilizes quicker than quickcrete.