Currently the Extension default namespaces page goes to great lengths to tell site operators and extension authors what namespace constants (numbers) to use for what things, which is great for anyone setting up a new site or writing a new extension. However, operators of older sites with site-specific (custom) namespaces can't currently benefit from this advice for their existing custom namespaces. Therefore, it would be good if clear documentation on how to change the number a namespace is assigned to could be added (including whether the change requires any maintenance scripts to be run, whether it impacts caching of pages in the renumbered namespace(s), etc), to this and potentially other pages (or a new page on the topic be written, in which case additional detail could also be added for situations such as number conflicts, splitting a single namespace, merging two or more namespaces, etc).