Well, I've done this. It's freaking COOL. Let me be more clear. I HAD it done by the dealer where I get the bus serviced (Bryant Motors, Renton WA, great shop). This was not a great idea due to the unanticipated cost, but I've now got a great system. In Washington you can have white lights, but you cannot have the yellow and red flashers. That's what I was told, I haven't actually looked it up.
The mechanics wired around the flasher relay somehow, but this was apparently more challenging than they thought it would be (probably due to the spaghetti of wires in the panel area--a MESS). They then installed two new switches above the driver so you can't inadvertently make it daytime for an oncoming driver. There are two so the front and rear lights are controlled independently (as flashers they all came on together). The rear switch also lights up the old panel light that illuminated when you had your flashers on, so you'll remember that you've got the rear lights on. The new switches and associated wiring added time to the bill, and I was somewhat shocked to find that this little idea of mine that they thought would be pretty easy came to about $300. But it's really the three hours of shop labor I think I got hit with... they were somewhat surprised, too.
I'm labeling the switches "THE SUN" and then below "FRONT" and "BACK"
I can light up the next county. Cannot be used on the road unless it's you and a whole lot of nobody else. Great for finding a campsite, though. Or signaling extraterrestrials, or ships at sea, whatever. Also better than caltrops for tailgaters, but you didn't hear that from me.