Just leave the Garage pier in place mate regardless of wall thickness.

The Kitchen which is obviously a add-on/extension may also have a brick pier to support the L/H end of wall plate ( the wall plate supports the Kitchen roof joists, likewise in the garage)

Both have little load on that type of roof, and are often just spanned off the wall plate.

Bet the Kitchen wall has not been stitched into the Garage brickwork???

If you retain the piers, and just throw up a stud wall then no need for any RSJ/Lintel