If you have decided that you need to outsource some or all of your proposal development work, now you need to decide:
Before you start to outsource work, you need to clearly define what you are expecting to outsource. Does it include proposal management, proposal writing, editing, formatting and production, red team review, strategy development, graphics development, or something else? The decisions you make here obviously depend on the availability and capabilities of your existing staff.
Remember, though, that multitasking just does not work as well as we would all like. (Despite the admonishment on the job description that says “must be good at handling multiple tasks and assignments.”) Various studies have shown that people are generally not very good at this; my own observation is that multitasking performance becomes much worse as the complexity of each task increases. So: having a proposal manager function as a writer, or having them try to manage several large complex bids is likely to fail. They are going to miss something critical. On the other hand, a graphic designer might work on proposal graphics for several bids in a given day – they just need to know the priority of the queue.