I currently use the AGPLv3.0-or-later. Ideally, copyleft-next itself would have an AGPL-like clause. Given that this is still a source of concern for some people, how about an (optional?) clause that would trigger AGPL-like distribution rules?

In SPDX terms, I'm guessing it would be a distinct license identifier: copyleft-next and copyleft-next-network