Looks like an interesting mod. I have thought about doing a "drl off switch" mod but not a "drl always on" mod.
Taking a quick look, it seems like it may be easy. Locate the D2 Daytime Running Light Relay and locate wire #12 light green with a red stripe.
Cut it and wire the side coming from the body ecu to the bottom prong on the switch. The center prong on the switch should go to the #12 light green with a red stripe. The upper prong on the switch would be wired to an ignition based 12V+ positive wire.
Thats a quick look and I will look at it more tonight, I gotta take off now.