One of the biggest cons is that above the tv is way too high for most people's optimal/comfortable viewing. There are several different opinions about the best height at which to view a tv, but generally when sitting you should be staring at the center of the screen or at the very highest at the bottom of the tv. Unless you have an unusually low-profile fireplace, watch tv standing or are like 6' 6" tall, a tv mounted above the fireplace is going to make for some uncomfortable viewing.

can you do search on previous discussions on the dilemma section of Houzz - you will see this often comes up. Bottom line, it is not a good idea as heat and a tv don't go well.

Try the TV where the sofa is now and float the sofa perpendicular to the fireplace where you currently have the big chair. Perhaps the big chair can then go where the TV was for a quiet spot for one. Or even better, pull the loveseat off the wall and put the big chair to its left flanking the fireplace.

Could you post a picture?