Could you post a to scale floor plan showing all windows doorways etc and all measurements clearly marked. I think new flooring and the removal of the other brick would be required if you chose to remove it . I think I would look at having a new FP installed maybe a see through one but not 4 sided and then just a simple vent and of course gas . You do not mention any thing about your style but you could do something like this maybe . I would need more info too as to do you need a FP at all for heating ? If not then maybe look at etanol FPs for the ambiance and no flue needed.

I would take it out. I'm sure there is a way to incorporate a fireplace and media wall that will fit the style of your home much better.

Remove the whole thing.

thinner like this? No. there are much better design options.

You could remove all the heavy brick. it's not vintage or even all that nice looking. (ditto around the windows)

at the very least, paint all of the brick)

you could try applying a heavy mortar wash, and then a limewash product to get this look

Or even this look. heavy gray mortar (german schmear) w/a limewash product like Romabio. remove the insert, your mantles, install a stone hearth,

limewash

remove the brick or tile right over it w/something like these

or some kind of stone. (this is beautiful

you could try wrapping it w/wood shiplap molding,,,,

Lastly, do a skim coat over the entire thing. Cement overlay,

roman plaster are two possibilities.

You could then finish it smooth, rough, paint it, whatever you like.

Why don't you look at pics of "double sided fireplaces" or 1970s double side brick fireplace redo" and look at all of the possibilities.

of course you could just rip out the whole thing. up to you. but as you can see by the pictures, there are some nice looking options.

my vote is for getting rid of it; those views are too beautiful to conceal even a bit!