My first reaction to the news was "really, that's the best Alabama can do?", but upon considering it further, I don't think it's completely outrageous that Kiffin might succeed here.
He only sucked as a head coach at each of Oakland, Tennessee and USC. He did well as OC at USC in the period after Chow. He did have very talented players to work with, but Alabama has some talented players too. As far as SC's offensive struggles with Kiffin as head coach, they've only really fallen out this year. In his first three years as SC head coach, they were 4th, 3rd and 6th in the league in scoring. Not very good, but not disgraceful. This year they came in 9th in scoring, despite having all of that talent, which is pretty shocking and really testifies as to how well he got his players to quit on him.
At SC, I saw a team that had only gradually came to have no faith in him or respect him at all, not a team that was running a broken system. Eventually they just couldn't give their full weight to preparing for and executing his scheme because they didn't want to play for him. At Alabama, he may have less of a detrimental impact on morale for the simple reason that he's not the dominant source of their leadership--Nick Saban is.
The SEC coaching fraternity seems pretty insular to me. I can't think of too many SEC teams carrying former Pac coordinators, and the reverse is true too, whereas there's guys from pretty much all there other conferences around the Pac-12. If Saban wants Kiffin as OC, despite all the negative things that have been said of him, and despite how his offense tanked at SC, it does say something.
The "modernization" aspect doesn't really add up. Kiffin's offense actually seems rather conventional to me. The offense Kiffin is taking over doesn't seem much different than the one Kiffin himself runs. A little heavier perhaps, more basic, more grounded and less intricate, but similar creatures. If he really wanted to get new concepts into his offense, it seems to me he should have brought in someone like Noel Mazzone or Scott Frost.
Even though I do not believe it is certain this hire will result in failure, it is surprising to me that it happened anyway. Alabama can almost certainly do better--it doesn't seem there's much of a potential to have it be more than a modest success, and could turn into a distraction if Kiffin's personality sows the kind of discord he's left pretty much everywhere he's been since he left SC the first time.