I don't know if you have ever been on a coaching staff(trust me, if you have not, it makes no difference at all)...I have been on them in different ways (insert sex joke here) I have been on as a new dork (old term for penis from the movie Porky's) where I did not know a thing, I have been on them as a guy with experience, I have been on them as a guy with lots of experience but having to take on knew duties and I have been the HC that has had to dish out assignments.
You ask, what will he bring to the table...everything he has ever learned. I don't think you actually understand your question, I think you are either trying to rip on Beck or you are claiming that Meyer knows everything about offense. Maybe I am wrong and you are really just asking...
It is a new set of eyes, it is new experiences, it is old experiences...I mean, are you asking if he is going to invent some new forward pass? Probably not.
I have had guys on my sidelines that have had years and years of coaching experience that sucked...I have had guys that had never coached before, ever, and came up to me during a game and said "Hey, I think you should try this, I think it will hit" and it did.
Maybe my answer sucks...I have no idea...but you asked "why"...I had a coaching class I took...the teacher was stud coach at the high school ranks...he said "I paid 600 dollars for a coaching video on the run and shoot offense, in the end, I only used one play out of the entire video, but it worked, almost all the time and it was worth it, even though my wife thought I was crazy"
Sometimes what seems like a crappy investment to others is a great investment to someone else. So, what does he bring? I think he brings exactly what Meyer is looking for...Like you said, a coaching legend...a coaching legend went and hired him. Meyer doesn't strike me as a guy that is doing anyone a favor...for no reason. The last thing I would say is this, NU just hired a guy with a totally average record, but, we sure think he adds a ton of value.