User blog comment:Deshiba/No counterplay/@comment-24953093-20140518043943/@comment-4022742-20140519140038

Well having to think about where and how to use your ult without getting interrupted is something that all the other champions that don't have unstoppable attacked to their ultimate abilities do have to deal with. You won't hear anyone say that Warwick is unplayable because he can get interrupted, or Wukong, Maokai, Nautilus, Nocturne, Pantheon, Sejuanni, Shyvanna. They are all engaging champions that bring CC to the table (some more then others) and initiate without the unstoppable mechanic just fine.

Would it require mechanical and numerical changes to their respective kits? Yes. Would it be worth it well, if the champion would get more interesting due to it I'd say... Yes.

As for Olaf, he's still a Berserker. But what can the unstoppable mechanic do that Tenacity can not? If anything tenacity will sort of bait people into putting Crowd Control on you to stop you, giving more room for your teammates to go ham. Now I'll answer my own question by saying that knock ups and Knock back effects would be hard counters. But I feel something like this should suffice:

Olaf instantly removes all crowd control effects from himself and gains XX Tenacity for 12 seconds. During this time, he loses the passive bonus but gains bonus attack damage and movement speed.

Any numbers would have to be balanced, but having 40/50/60% scaling on that tenacity would leave you at 33/28/22% duration of any non displacement cc, provided you buy tenacity in game and max out the Defense tier. A 3 second suppress would only affect you for 0.66 seconds.

But ye, it's nice to dream :-/