The initial reason we've chosen to create an "all-in-one" ISO image was to simplify further configuration of an automated installation with PXE / Answerfile.
We tried driver disks before, though in our special case of mellanox-mlnxen-alt and hardware without any other NICs, I believe it always ends up requiring manual intervention. I haven't found a way to load the driver disk in the installer that is not connected to the network.
I think, even though my approach requires a bit more effort, it can still prove useful in some cases.
