An Apache/AGPL dual license is basically the same as Apache-only (thus eliminating all the benefits of AGPL), except it would allow someone to create an AGPL-only fork (which would probably hurt the project).

You can make an AGPL fork anyway. You cannot relicense other peoples code, but you can make all your changes in your fork AGPL. That gives you as most user freedom as possible for a permissively licensed project.