It would be helpful if we could see what happens behind the sofa with the platform and steps.

Looks like the platform conceals ductwork. You need to investigate whether this is supply or return.

I think I would not do a bench but select and arrange the sectional seating so that it looks built into the area and not so chopped up.

This is strictly for design purposes. The ducting runs under the floor and is not running through the platform. There are vents on top that are connecting to ducting below the floor itself. That vent on the side is not a return - looks like just to be able to access the gas line for the fireplace and the ducting below the floor.

Honeastly do you love its quirkiness? I would just take it out ans replace it with soame proper seating.If that is impossible rempve the carpet tile it and graow some awesome plants there with all that light . The house itself is kind of interesting is that stairs again behind the sofa, maybe post pics of that too.You definately need to get some clue as to why these things all over . Maybe try to get the original home plans then you can see what might have been done.

I’m not a big house plant person but this area really calls for it. I’d get some large round planters with sizable plants in them. Or place a sculpture here. Or toss some chunky big throw pillows and make it a place to lounge with a book.

I like the idea of large plants but honestly, you can just leave as is.