Last time I checked, there was a way to unlink your Youtube account from the Google one, so it may worth a check, but no guarantees here as Google changed a lot on this front lately.
Just tried it, and you can indeed unlink the accounts. But you can't login with just a youtube account. You need a Google account.
Still useful to relink to a throwaway account instead of the main gmail account. But I'm not sure the multiple account will let you stay logged in correctly..