First you need lights with dual filament sockets, or rig an led into the existing lights.
Then just tap in to the headlamp low beam/tail lamp circuit and wire the running lamp filament off that and leave the directional filament wired as is.
This seems simple enough (famous last words). I think I'll give it a go this winter.
What I'd really like to find are some mirrors with integrated signals that will fit on my ST2. Most I've come across are more cruiser-appropriate...
Thanks all for the feedback.