The title says it all. In my experience, Pipewire on Garuda works flawlessly as a drop-in replacement for Pulseaudio. On a fresh install, it's as simple as...
Removing pulseaudio and it's dependencies
Installing the pipewire-pulse package
Rebooting
So, seemingly all you would have to change for the ISOs would be to just use pipewire-pulse instead of pulseaudio.
I imagine this will be done "at some point". PipeWire still has a number of rough edges, e.g. Bluetooth outputs will randomly stop playing and require some toggling to get working again.
As you say, for people who know what they're doing it's a trivial change until it's made the default.