Help with my story, realstic promotion letter needed?

If I was asked to draft such a letter (and I frequently need to in my line of work) I would first need to know more about the company. For example - how large is it? Is there a close relationship between the management giving the promotion and your guy OR is it an offer coming from head office and from people he does not know or usually work with? This will effect the tone of the letter - too formal and it would sound strange in a small company when he knew the people offering. For a small operation you would be more likely to get a fairly informal letter full of praise enthusiasm and congratulations but with a one page (maybe only one paragraph) formal offer just for your guy to sign and return to indicate his acceptance. With a larger company and no strong personal relationship between the promoting managers and your guy - the letter would be much less chatty, much more formal and to the point - maybe attaching a detailed copy of the new job description and detailed terms with a copy to sign and return.