Oh, okay, may need to clarify some more. If you get a new 2 seater in place of the 2 white chairs, fine, but no blue chair at all next to the 'new' 2 seater. Won't be right with a blue chair too. So what ones are you planning to recover?. If getting rid of part of it, not understanding. 2 different styles placed next to each other won't look right. I wouldn't like old blue fabrics next to new fabrics or next to 2 different styles of furniture. New 2 seater and old blue chair next to each other, not good :)

I love a QUALITY paint job. Few people know the ins and outs of a quality paint job but, a seasoned painter for INTERIORS will have many techniques and processes to dial up the end result. I love my painter and I listen closely to his advice and he is so expert (40 years) and good that he makes it look effortless. BUT IT'S NOT. Will find and post favorite picture of painted trim here. I think the secret is style and proportion of trim and then the quality of the finishing. Did you know most paint curing really needs 2 to 3 weeks to set up as a really good tough finish? "In a hurry" is the curse we mostly experience for improving interiors. I wonder sometimes how different things would be if people took the right amount of time to do things in the time frame related to that finishing task!

Treating the sliding doors as a modern insertion and keeping the rest traditional could be striking. However, what does the house need from the interior? If it needs more light/views opening the house further with larger windows could be great too. An important detail for the sliding doors will be the casing (trim) - whether modern and intentionally different or matching the rest.

Well, for lack of a better idea, since you find it a drafty little space. I'm assuming the draft comes in on the right? Most of the necessities in the area are located of the left side; i.e. vent, thermostat, light switch etc. What I would do I think is caulk up the drafty spots, maybe even add sized poster board wrapped in batting I covered in a gorgeous fuscia with diagonal grosgrain ribbons every which way covered with a heavy velvet to be attached to the area above & below the window. (Of course remove the drapes that are hanging in there). This for the purpose of using it as a pin-it board for notes. Attach a table height board covered in felt to carry across the full width of the little room. Leaving just enough space for a comfortable little antique desk chair. Paint the back wall a bright cobalt blue, paint the ceiling a silvery pearlescent white. Find a way to attach a clip-on task lamp. And stretch a heavy duty enough wire across the top of the opening and complete it with a heavy doubled velvet drape with a drooping valance. Place a swag with fringe & jewels on it to be closed when not in use. Voila intrigue is yours!