The WIP schedule is the plan.
Nine times out of ten, when an owner tells me they don't have a written plan, what they actually don't have is a clean WIP schedule. Fix that first. A current, reconciled WIP tells you what you're going to bill next month, what your real gross margin looks like before year-end surprises, and which project manager is routinely over-billing. You can build a three-year plan on a good WIP. You cannot build anything on a bad one.