Original author of the above script. I also have an updated version with some fixes but it is annoying to chase around the changes being made to PiHole so I kind of just gave it up.
I'd think that a feature request is the better way to go about this. There are only a few changes to PiHole that would make the install script run directly on asus-merlin.
- A new installation target with the opt package dependencies needed
- A variable to globally control where everything is installed, /etc vs /opt/etc vs /vffs/opt/etc or whatever
- The configuration of the bridge which is really just a trivial one liner.