AGH is designed to be installed and updated as they patch things. Both the stable and edge branches require this. The opkg version is not my creation but its listed here to up its profile and due to collaboration between James and I in the progress of this project.
AGH is still fixing issues and hopefully we will be able to have a much better experience via opkg as we are in the end going to replace dnsmasq and dhcp with AGH completely and thus scripts etc won't be required.
However until the AGH team updates a few things this cannot happen.
They are also looking at reducing the size of the AGH binary. James has found that compressing it with UPX improves the size.
Further up in the thread is a list of issues that were filed. unfortunately it seems that most of them have been pushed to the 109 release schedule.
Until these are fixed/closed then the only real option we have is the edge install to keep AGH added to OpenWrt. In time opkg installs will be the way to go and I'll happily retire this thread.