I'm against backing tracks. If it's more than reverb, then, I'm against it. IMO, he should hire a backup vocalist to sing with, to do the low parts. Or go without the vocal part. Sorry. I'm a huge Axl guy but IMO live shouldn't be perfect.
If you have to hire more performers, do so. Like country artists do. When they perform live, there are enough musicians and singers on stage to do a fair representation of what was on the record.
Axl's got enough musicians but IMO he should go ahead and hire a backup vocalist instead of having Pittman play vocal recordings, or whomever does it.