If you look at the Man Utd scenario, whoever succeeded Fergie was either going to be great or, more likely, on a hiding to nothing. We all know how that went.
I think Arsenal are playing a strategic game in going for Arteta. Like Fergie whoever follows Wenger has big boots to fill.
If Arteta is a sucess then it was a master stroke. If he fails then he was being used as fodder, the buffer in between Wenger and the next guy, who will, in all probability, be a really big name.
We don't have such problems, we've had enough fodder to last a lifetime. We just need a manager.