Your options will become more clear when you peel off the drywall and see how the wall is framed. It's not a big deal if the wall is structural, but that will affect the cost effectiveness of your design.

If you tear the wall down, you'll lose the flexibility and value to use this as a guest room or media room in the future. Have you considered a skylight in the new office? In addition to removing the door, it looks like you can widen the doorway opening to allow more light in and obviously, painting the walls a much lighter color will brighten it up. It looks like you have a chase in the left corner?

Instead of removing the wall, I'd look into adding a window or skylight to the room, and then replace the door with a clear glass one, pocket door, or interior barn door.

Thanks for the input. Unfortunately adding new skylights or exterior windows is complicated by current condo rules - so that is not really an option. My preference would be to put in serval skylights in that room - this is the non-approval workaround

In that case I would leave the wall alone and put a barn door in the inside of the room. You can leave it open for your office so you get some light inside, while still maintaining a room that can be enclosed if you or someone in the future wants to use it for another purpose. Paint the walls a light color and add lighting.

You have a light switch and a potential stair / fall hazard to consider so you might want to CHANGE the wall rather than remove it -- create a half wall bookcase or cabinet with either solid and/or glass doors -- then repurpose the space, perhaps into a home office. You could even keep posts and a short span of wall along the pony wall (or cabinet) as needed in order to keep the light switches and outlets where they are while still opening up the space.

https://www.pinterest.com/pin/31947478576415417/

http://elephantbuffet.blogspot.com/2013/02/how-to-keep-from-falling-down-staircase.html

Would definitely want a smaller room a light color. What size and shape is the room behind the wall?

Can you post a to scale drawing with measurements indicated and door location indicated and ceiling height indicated?

Or you could try a steel framed glass parttion and door to allow light in, but still use as a room.

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How you are going to use the room matters.

You could leave an opening in a half wall equal to the size of the current door. If this is to be an office you want open but also don't want any person or pet walking up to you while you're focused on your work, you might add a half door or turn the door you have into a half door.

Your half door could even be a cabinet on a hinge -- six or eight inches deep -- or leave the "shelf" atop the (bottom half ) door overhang into the room and hide a slide bolt inside the room beneath the overhang.

https://www.ebay.com/itm/333852582069?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=333852582069&targetid=1068323854230&device=c&mktype=pla&googleloc=9011027&poi=&campaignid=11614425341&mkgroupid=113541562975&rlsatarget=pla-1068323854230&abcId=9300456&merchantid=6296724&gclid=EAIaIQobChMIio2F3biN7wIVQ7KGCh0lmQA2EAQYAiABEgKV0PD_BwE

I'd put in a french door and paint the room a very light color.

I noticed that there is a leak in the ceiling of the room you want to open up. Look at the drywall joint that has popped...