The bottom link shows someone using a microphone pickup without the feedback problem. He does this by cutting the high frequency on the reverb and just leaving the low frequency. He says he has two microphones inside his guitar. Any thoughts? Is this doable?
His discussion of this is in between 6 minutes and 7 minutes.
I'm fairly certain he's using a blend between the soundhole pickup and the mic pickups.
Microphone blend systems will work, however, most of the signal going to the TWA must be from the piezo or soundhole pickup.
You can blend a bit of the mic in, but too much of the mic signal will result in feedback.
I'm sure that maxing out the Hi Cut would help a bit in terms of microphones, but if it's a mic only system, you're still very likely to experience feedback.