I have to laugh because I just went through a similar situation. The one's you see with no gadget boxes are most likely hiding somewhere in the house. They have been wired through the walls. My BIL has his in a closet. When he changes the channels he has to point the remote near the closet. DH ran the wire inside the wall to come out behind a bookshelf where our boxes now reside.

I'd put it beside the washer/dryer and above a counter height wine/coffee cabinet. Mount it on a swivel mount so you can adjust the angle as needed. Barring that, B is the best option. A won't work if that door sees any kind of use because the chair is right in the traffic path.

How many people are in your household? What else do you need to put in that room? I would consider putting the tv on the left hand wall with couch where you have the tv in your plan. Put the tv on a console so it can be turned toward the couch for better viewing. The you could have additional chairs closer to the sliding doors for more people to sit when needed.

If you're not willing to move the furniture in order to access the only other plain wall in the room, then what else can you do? we don't have a magical answer for this. putting it in the corner looks weird. So, that leaves the fireplace. Remove that large mantle you have and do something different. I'd also do something w/that brick. that fireplace could really become a focal point. I don't think you're seeing the potential of that room of yours. some other ideas what's wrong w/either of these? I think they look great. BTW, if you did closed cabs beneath the windows like they've done here, you'd have all that storage for toys and stuff! (ditto if you did hinged benches under the windows. you could hide all of the toys) they don't even have to be built in. just make them to fit under the window and top w/pillos. I love this idea if you have the two windows. this is about the size of your fireplace. a larger tv will work fine. another one w/o windows, but gives you an idea what's to the right of the fp? another window? if not, you could try this: If there is a window to the right and you really don't want the tv above the fp, then consider removing the window OR, put in a smaller window and raise it up towards the ceiling. then you could do something like this (the window would be more of a transom style where this light would be) this is what I mean by changing the furniture. imagine the tv is on the wall across from the fireplace (and those chairs aren't there)