Opening Up Masonry Fireplace

[Fezatron]

Hi fireplace gurus. Forgive me if I use the incorrect terminology. I’d like to expand the width and height of my fireplace opening but have run into an unexpected potential issue.
My fireplace “had” a C shaped section at the front (looking from above) next to the opening on both sides. Pics below. It has an arch in the face and then the infill below the arch and then a normal course of bricks. It was here that I would put a galvanised steel lintel so that I could open up the brickwork. The facade is one brick thickness in the face until higher up in the chimney. I’m not sure of the logic behind the C design as it only went up about 9 courses and had some bricks just sitting on the top. (One had fallen in and the cavity was filled with soot and bits of mortar). The outer facade has a wythe sitting inside it. This isn’t connected with bricks at the front and back.
So my question is this : the arch directs the forces of the bricks above and some laterally outwards. Is this C section design to provide some lateral strength inwards to counteract the lateral outward force from the arch? If I remove the inside part of the C section will this be too much force directed outwards onto the the facade and my fireplace fall apart? Any help appreciated.

 

[Fezatron]

I forgot to add that the facade and inner wythe bricks are different sizes so removing some bricks and replacing to tie the 2 together isn’t possible.

 

[Woodsplitter67]

Just a question.. why do you want to do this. Is the fireplace running incorrectly. Will you be trying to put in an insert or a free standing wood stove..

 

[Fezatron]

Yes to put a freestanding stove into the fireplace.

 

[bholler]

Yes to put a freestanding stove into the fireplace.

Make sure you still have enough masonry left to give you proper protection to the combustibles on the other side. If you only have one course of brick that isn't enough