Simply put, if you keep tweaking the best proposal in your department's history, you are virtually guaranteed to get the best proposal you can possibly get. Have a proposal workflow that everyone in the sales team uses, and you'll have a system that allows team members to exchange ideas and advice, as well as accumulates a database of reusable and searchable proposals.
In reality there are many cases where there is no time to get that peer review done. After all, documents are destined to be completed just before the deadline. So it's realistic to assume there will be times when a member merely registers a proposal that has already been submitted to the client, thus doesn't have to go through the peer review step.
