Big Bru fan, but I think it's a long shot.
The lack of pro bowl appearances may be a factor. Urlacher made it in with a career the same length with 11 more INTs and 300 more tackles. His teams were far less successful. The difference is he had 8 pro bowl years to Bru's one. He was the poster child for Bears defenses for years. Bru was part of a defense that never wanted a featured player, and quietly did his job. While that role is great in terms of team building, the Hall is looking at individual stats/achievement.