I do see the value in having the feature, as anything that can save time is great. You're right that it's not a complex feature. The issues that need to solved when implementing it are: 1) where does the setting live, and 2) how it is configured. As with anything, the devil is in the details.
For lack of a better place to keep it, it could go on the settings dialog, maybe under behavior. To configure it we'd have to decide where it will be applied, eg bones, slots, etc and decide if those places each get their own setting or use a single setting. For how the settings themselves work, it could be a text box where you use special tokens like %n for the next number, or %a for a-z, or it could be something else. Having preset patterns is probably easiest, eg starts with or ends with, number or a-z, separator - or _. However it works needs to be clear to the user. To use such patterns we need some way of detecting the pattern when looking at existing values so we can determine the next value (that is why preset patterns are easier). Also the resulting name must be unique, so there are requirements that must be enforced on the patterns.
