I don’t quite get what all the trouble is? For my use case the users I whitelist are in my database, so if I need to get their Twitch ID’s I can just type in all their usernames, press a button, and have the full list of ID’s to copy paste.
Even if I didn’t use a database, the Get Users endpoint allows you to enter up to 100 usernames, the same as the max whitelist! So just enter your names there, press button to get results, map results to just ID, then copy/paste into the dev rig, all of which could be mostly automated. It would take just as long as entering the names into the dev rig would (ok, maybe 200ms longer due to the API request) as either way you would have to be entering usernames and unlike using usernames as a whitelist value using ID’s doesn’t have the same security implications.
You also mention about clearing the whitelist on every new version, that’s counter-productive and could easily lead to people who should be on the whitelist being removed and then for whatever reason not being re-added.
The point of using ID’s is that it will always be consistent and so should always be used. The page could potentially add a username to ID tool built in to it for people who for some reason are unable to use all the other tools available to them that do that already, and then you could just copy/paste from the tool on the page to the whitelist.