If you decorated in french country the railing wouldn't be dated. :) Unfortunately, decorating in french country has to be the most expensive decor!

This is a beautiful room, with lots of light! With the bookcases I do see the potential for a library/ conservatory. 4 armchairs around a round table or ottoman would be great. You can also float 2 love seats. If 1 was against the wall between the bookcases, and the other was facing it, this may allow for sofa table console. With some kind of coat rack now you have an entryway. I would create an entryway along the wall with rail and straight ahead to small area by kitchen. Your lighting options are fine, recessed cans not required. Houzz has nice articles on how to use an unused room too (crafts, yoga, office?). Unlined white curtains or sheers will add privacy. You could mount on a double rod and put your colored curtains outside to close at night. Finding an inspiration color, pillow, or image might help it not be overwhelming to pick colors. Keep us posted, and I would like to see the hickory chairs!

drblount, the chairs around an ottoman is where my vision was heading as well. I think they would have to be small in scale and was wondering if I might be able to get away with 3 chairs of if that would look odd. I'll have to do a search. I've always loved the look, and have some in my idea book. I did look at and sat in this chair:https://www.crateandbarrel.com/drew-small-swivel-chair/s305270 in the color 'Lake' which is a deep blue, but it really is more than I should spend. I do like that is swivels. I'll look and see if I have a photo of the existing chairs.

I was also leaning toward sheers, perhaps a light linen. I lean toward organic - love wood/natural fibers.

(oops auto correct--that is, I googled the chairs)

Just some random thoughts:

a) don't think you can push the bookcases together without altering the molding at the top. An alternative is to separate them and create a bridge over top which could span a love seat...add lighting into the top of the bridge.

b) I'd group the furniture around the window and the solid wall so as not to have to put a traffic pattern through the center of the conversational cluster

c) recessed lighting can be unattractive unless it's used near the edges of the room with deliberate purpose to highlight drapes, artwork, etc. They do make smaller cans now too that I think are better looking. But good lighting is essential to making any space look well and functioning well. But if you are having electrical work done, you might want to do a good layout and then look into have a floor outlet added so you could add a lamp and side table to a chair or two that would float in the arrangement

d) that large window is lovely but looks like privacy would be an issue at night so consider drapery treatments for it and how that might work with your plants. Also, depending on what region you are in, insulating needs might be an important consideration.