Wordbiker

If it were my frame...I'd have it welded.

Although the frame may be overbuilt for the use it will see, losing the strength of that brake bridge can transfer loads to a different part of the frame that was never stressed before, leading to a break. I have seen aluminum frames that had more than one break: the first crack and the second where the stresses were transferred to, broken clean through. Fortunately for you, steel is the most repairable of materials and any good welder (bicycle experience or no) that understands the material should be able to weld it. Find someone you trust and ask their advice on which method fits the application.