We found this to be a real balancing act. The compromise was to require that all departments use a common cover page (containing requirements for approvals, unique numbering, etc.), produce a separate work instruction on how they exercise control of their WIs and include a couple of small sections in each WI explaining the purpose and scope of the document. Beyond that, they're free to write them however they see fit. By doing this, each department has the freedom to construct the WI in the way most useful for themselves, while the initial feel and look of all WIs has some consistency.
I write this as if it's a done deal. Actually, we're still in the middle of implentation and finding some resistence, but we're trying to stand firm.
