Late to the party, but here were my actual Thanksgiving experiences:
1) The brine. I used a Butterball 14 pound pre-injected turkey. I made the brine full strength with salt (1 cup kosher salt to 1 gallon water). I have been doing the full-strength brine for decades on pre-injected poultry. And it has never been too salty, not even close. I think "brining a pre-brined or pre-injected turkey will make it too salty" is a myth perpetuated by "theories", not people who have actually tried it. Note that anything Butterball says is to be taken with a grain of salt (no pun intended). They are a huge company, with lots of lawyers, and their advice errs on the side of cooking the bejezzus out of the turkey, and keeping the salt level to a point that if someone on a super low salt diet drops dead of a heart attack at the Thanksgiving celebration, they will not get sued.
2) My 14 pound turkey took 4.5 hours to get to 165 in the breast. I am using a #1 (with an analog controller) turned all the way up to 250.
3) Holding time. I put my turkey on a sheet pan, covered tightly with heavy-duty foil, and left it on the counter. After 1 hour, it was still piping hot, too hot to handle with bare hands. So as far as food safety goes, I think you could easily hold it this way for a couple hours, even throw a towel over it for extra insulation. It should still be quite warm after 2 hours, and it has not been in the danger zone long enough to cause problems. If you know if will be more than an hour, you should also be able to hold for 3-4 hours in a cooler (wrapped in foil and towels).