It would look odd with just a curtain rod across the void. You could get a pelmet made, or fill the void above the curtain with a shelf or cupboards though this will involve a little disruption. I would avoid plastering too as it is a messy process that takes more than one day and needs painting too. You may still want blinds on the windows for light control but soften the whole look with side drapes as you asked for. Shutters could also work either way but they are pricey.

Hi You can also get a gyprocker to make this up as a premade L shaped bulkhead then it can just be attached with some angle on site. We do it all the time for coffer ceilings. Try talking to your local ceiling installer. Cheers

There is not much room for block out curtains to stack on the sides of the end windows, a better option would be to use screen roller blinds for privacy during the day and Roman blinds placed over the top for privacy at night. Roman blinds are great if you want to bring colour and pattern into the room and add a playful vibe. Image - Silvia Rajek Interiors Alternatively you could run a rod across the whole wall and have sheer curtains ( closed most of the time) and have block out roller blinds on each of the windows for privacy at night image from Pinterest

You will need double tracking or double rods . These will use double brackets which extend out further .If you are on a budget then Spotlight or Bunnings for the rods and Spotlight will have ready made sheers and classic curtains . I have just ordered double rods cut to size from Curtains4Australia and their prices were good . For the curtains and blinds look at BlindsOnline and their huge range . They will send samples of your choice out to you and have a range of fabric prices . If you need help measuring or any questions , then you can ring them and speak to someone who will explain and helping give you options for your window .I have used them for five rooms so far and they are spot on . I will be using them for the rest of my house except for the main sheers as I am after a particular shade and weave . ( I Seek Blinds - I haven’t used them yet ).