The Key Schedule I attached was sent to us via our FM Group when our Stake Center was re-keyed in 2005. It has provided our stake with valuble direction on who should be issued keys. I have not seen any other document which lays out who should receive keys. While the document may be dated, and does not include callings such as the STS, it does include most of the callings in the wards and stake. When someone requests a key for a calling which is not on the list, we discuss it with the appropriate bishop and ask the stake president to authorize the key. If they both agree, then I contact the FM Group and a key is issued. This has worked for our stake and we have issued keys to members with callings which are not on the list such as: the STS, seminary teachers, organists, and building schedulers, to name a few.
The fact that it is on Church letterhead has assisted us in issuing keys. Everyone wants a key. When we show them this document and that their calling is not on the approved list, then most members drop their requests. For those who still want a key, we discuss it with the bishop and stake president as outlined above. If we were to give keys to everyone who thinks they need one, then it would be unmanagable. This schedule has been very helpful in keeping the keys to a managable level.