I think this already exists? I use it all the time, unless I’m misunderstanding what you’re asking for.
Go to Devices, pick a device. Click the pencil icon next to the device. Enter a new name, click Update. It will ask you if you want to rename all of the entity IDs, click “Rename” to do so. If the original name of the device has a sub-string match with the entity IDs, it will rename the IDs and their friendly name, according to the new name. Is that what you are looking for?
Note that for some reason this is considered “advanced” functionality, so you must have “Advanced Mode” enabled in your user profile in order to get the entity ID rename prompt. If advanced mode is off, you won’t get the extra prompt.