This is the systems that many use when doing expensive layups. It is also the basic principle of moulds for RTM-light tooling. (the sealing of the mould is never as airtight as you would like it to be, using the reusable seals, but the double vacuum solves this problem.)
You need 2 vacuum levels, however, so you need an extra pump or some other gadgets to get 2 levels.
