IMO, with all of the years experience he has of breaking down film. I wouldn't doubt that Ray has a world of knowledge on how to attack offenses and/or stabalze them.
People say Ray Lewis has great instincts, but instincts really means you know what an offense is capable of doing, because of your dedication to your craft, in reviewing film, and figuring out formations, tendencies, checks based on certain defensive looks, etc...
Ray Lewis doesn't just show up and walk on the field, liek it seems from the eyes of the media. He's been coaching behind the scenes, and on the field from the MLB spot for a long time...
Furthermore, the Ray vs Ed is a silly question IMO. Do we think Ray hasn't shared with ED what to look for, and vice versa. Those guys are the co-captains of the defense, and are close buds for several years, so I don't think one knows that much more than the other; they've seen it all, and shared it all with each other.
With all that said, I think they both can coach, why not?
But they need to transition into the management/facillitation end of things. So I doubt they'd jump right in as a DC for any competitive program. Should definately help out, even if it's just being a fly on the way in the room though, and is asked give his thoughts...