@Calvin Kwan - Thanks for correcting me on the OMI situation! That is obviously much more appealing.
You're correct that you don't need to change the lease when a new tenant moves in, you can just add an addendum. As long as they are added as sub-tenants via the addendum who will then pay rent to the master tenant who then pays the landlord, you can raise the rent after the master tenant moves out and you'll have better accountability like you said. I may have overstepped when I said don't add them to the lease, what I meant was don't create a new lease where they are all equal co-tenants and don't add them as co-tenants to the original lease as they will have the same rights as the original tenant. Be careful of the language.
That said, if the lease allows subletting do you know if you can require the current subletters to be added to the lease as sub-tenants w/ the addendum or is that something that you need to make sure you catch when a new sub-tenant moves in?
@Eric Chang - What does it say in the original lease with regard to subletting or adding new tenants?