I think the Titanium coated bits are crap, and extractors as well-for anything larger than 4mm or so. I have a few cobalt bits I use for broken bolts-on a Maico footpeg, I just drill it all the way through-slightly smaller than the threads-carefully. I can then pull out the trash with a 12 ga bore brush, and chase lightly with tap( be careful-every time you"clean out" a thread with a tap you enlarge it-thread chasers are available for this, being slightly smaller than the tap).
I like the copper pipe/mig weld idea-or weld a nut on it. Either way the heat will loosen it up. Unfortunately, if you have a freshly painted or powdercoated frame, the heat will burn it up-which made me do the fix I did on the Maico. BTW even if you bugger the threads, you can helicoil it.