The machinist in me says: This was my first thought. Then looking closely, it can be tig welded then, clean up the bore.take mine to the local Machine Shop and have my buddy do a "Bore and Sleeve" to repair what I phucked up.
In my world, making a bushing would be the easier way, (if the case wall is thick enough) but either way, the case would need to go on a mill. As there's really no other way to get a true inline bore alignment with the hole.
The wall thickness is so thin, a bushing would be super thin and prone to cracking. I would shoot for the tig / machine fix.