I think that you should only consider sight lines. In your case everyone will be coming in the door and presumably looking dead ahead. you'll get the most bang (since I assume you'll have some fabulous fixture in your entry) if you centre the lights on the door. Also a centred light viewed through the transom windows above a front door is a great warm greeting from the street (if your door is surrounded by glass). I went through the build process recently myself (moved in two months ago) trust me, you can't over think this stuff. There are tiny details all over the place now that I wish I had given more consideration. They don't spoil the experience of my new house, it's not that bad, but they do draw my eye in over and over and over. One of those niggling issues is my dining room light fixture which is centred on the dimensions of the room per plan, but does not account for the fact that the dining room opens to both a hall and my foyer so visual appears much bigger.

I would also tear off that mantel. If a new stone veneer is not an option, at least paint the bricks the same color as the walls in the room. Finally, put some edging or moulding on the top and side. What a great place to hang one big clock!

I'd create two separate areas, yes one, smaller one, next to the windows-two armchairs with a table between them. probably would go with something legged..more visually light, as to obscure windows the less..or give an impression I'm obscuring them the less:) another, bigger one, for TV watching..a sofa..an angled chair on the right much like you have now, but looking smaller..I might consider doing smth different since several chairs in the room..maybe a rocking chair? I might also go for an ottoman instead of a coffee table-can serve as additional seating if needed. I might also find a garden stool as one of the side tables-again, opportunity for additional sitting, if a lot people use a room at once. Round shapes will also break the lines of all the rectangular furniture, so I'd definitely take it into account when shopping. I also might do something patterned to add interest..say two armchairs, or an ottoman, or a chair in bigger sitting area.. Rugs would help to delineate different zones, so another idea to consider. Pretty room. Once you get your balance right-full of potential to be very cozy.

A ceiling fan is a good idea with a fireplace -- could you use multiple smaller fans with lights to create symmetry ? Or, could you use just one fan centered in the room but use multiple recessed lights around the room creating a square/rectangle around the edges of the room near the walls?