We would need all the dimensions of all the walls and openings in order comment or do a layout for you.

When not a bunk room, how will the den be used? Tv? Reading? Studying? Doing household records? ’net surfing?

How often will be it used as a bunk room? For what ages?

Additional measurements attached.

We're working with an architect - just thought we'd put it out there....

Why is a barn door so awful? For the most part it will be a den. With guests staying about 15-20% of the time....

So still missing some dimensions, but possibly move the door to the bathroom to allow for bunk beds. You may want to consider a Murphy bed style the folds up when not in use. You might look to European manufacturers that may have a smaller footprint for the beds and apartment sized sectional from Pottery Barn or Restoration Hardware. There are all kinds of sleeper sofas now the fold out differently and don’t take up so much space. I’d really do some research if you haven’t already.

How many people do you need this room to sleep? How will it be used when not housing guests?

Barn doors allow a lot of sound and light through. I would consider French doors or even pocket doors for guest comfort.

What age are your houseguests? If they're adults, a bunk bed may be far from ideal. I think a pull-out sofa or even a Murphy bed would be better.

Barn doors give no privacy. Either ruse really good, heavy pocket doors or French doors for this room.

I can't really see the layout being very comfortable as a den or as a guest room. Is this your only place to watch TV? If so, then I'd make it a proper TV room, skip the bunkbeds and chaise, and just put in a good quality sofa bed or trundle day bed.

That is not architect designed. Obviously.

With a narrow room why bother with a sectional at all? It just blocks the room visually and physically.

It is like a bucket with only 15-20% of the bottom missing. What's wrong with that?