Bleu, are you a property lawyer? if not, you should check with one and ask them this.
I own a property which i give to an agent to rent, i get rent from the agent who gets rent from a tenant THAT is subletting in itslef.
As I already mentioned in my answer: as long as there is a contract, anything can go into that contract.
What is illegal is to sublet without a contract.
Get your facts straight.