Feature to hide existing address book users from share filters when email already in system account

Feature to hide existing address book users from share filters when email already in system account: When sharing, if the recipient is part of both system accounts and address books with the same email, autocomplete suggests a duplicate. It would then be nice to be able to limit the proposal to the system account only. This would prevent the user from being able to share by email (possibly with a generated password) when the recipient has a nextcloud account.