TL;DR at the end for all of you who happily do as your told and don't bother to ask the question "why?"
My main has been Kennen for nearly three months. I've tried a few strategies with him, and of course learned quite a bit through trial and error (immediately followed by getting mauled).
Kennen's stuns are fight-changing and have potential for initiation. The problem with playing a tank Kennen is that tanks initiate. Initiators take aggro and get CC'd, focused, etc, and are expected to survive and continue to be effective. If Kennen lightning rushes first (which is, in my opinion the most effective initiation, in most, but not all circumstances), he can potentially mark every enemy champion, before they have a chance to scatter (because people scatter when a ball of lightning charges directly into their group). Following with slicing maelstrom, Kennen is perfectly set up to stun every enemy character with electrical surge, and finish off a player with thundering shuriken+auto attacks, or use thundering shuriken to apply a third, stunning mark if one of the first three marks somehow misses.
There is a major problem with Kennen initiating as such. If Kennen is stunned or otherwise CC'd while lightning rushing in, he loses most (if not all) of the first marks that would have been easily mass-applied to the enemy team. While slowed, Kennen is very easy to avoid, and the enemy team will have time to scatter, making it practically impossible to mark more than one or two champs. The second step, slicing maelstrom, then only applies one mark on each enemy, at best two on a small number, while the goal is to put second marks on as many champs as possible, if not all. The third step, of course, only gets a second mark reliably applied, while it could (and should) have landed the third marks/stuns. In this scenario, only two enemies reliably get stunned: one by thundering shuriken, and one by a charged autoattack (assuming one is available). This is such a waste, because Kennen can stun the entire team if he maneuvers correctly.
Of course, if you use the flash+ulti initiation that's not a problem, but you still must use lightning rush to apply the second marks, and when your ulti goes off the enemy team is unlikely to stand still inside your bubble. When they scatter, you have to decide whom you will lightning rush, and will not likely apply the second mark to every (or at least the majority) of the enemy champions. When you surge, then, fewer enemy champs will get stunned, and you have no escape (because rush is on cooldown) when the enemy team's stuns fade.
As such, Kennen is a poor initiator. He has to have all the CC applied to other characters so that he can lightning rush mark as many of the enemy team as possible, because once the ulti pops, anyone he has not touched with lightning rush will not get stunned when lightning surge is used.
I don't think Hourglass is a good item for Kennen. In order to ensure the maximum number of enemies get stunned, Kennen needs to be able to move his ulti bubble to mark any enemy champions that may be standing outside it when popped, such as Ashe or other ranged champs. If the enemy cluster is close enough to me, I will ulti+lightning rush at the same time so that I can get the stuns off that much sooner, and while rushing, chase anyone who may not be inside my bubble, to make sure they get a mark. Once I have marked everyone, I surge, and the stuns land. Hourglass requires me to be perfectly placed when I pop my ulti, and if anyone manages to escape the bubble before being marked, or are not inside the bubble already, I have failed to stun them when I finally am able to surge. Two seconds is plenty of time for people to get out of range.
TL; DR: Do not initiate. Wait for CC spells to go off on your teammates. Make sure melee champs have decisively engaged. Lightning rush to mark as many enemy champs as possible. Pop ulti and maneuver as necessary to place second marks on as many champions as possible. Lightning surge to apply third marks/stuns. Finish players off with auto attacks and thundering shuriken. Survivability items need only keep you alive along enough for you to get in, blow your load (of spells, you pervert), and get out. Do not stand still. Ever. That means no Hourglass.