I was considering this build on AP Kennen,
Boots -> Sorcers Boots -> Teleport CD Enchant
Hextech Revolver (sustain)
Rylai's Crystal Scepter (tankiness and slow)
Haunting Guise -> Liandry's Torment
Abysaal Scepter (mr and more m.pen)
Void Staff (40% m.Pen flat M.Pen goes after this is calculate)
Upgrade revolver to Hextech Gunblade (or sell revolver for Death Cap)
From what I read, Liandry's applies after the slow from Railays Crystal Scepter.
With 9 points in utility you can get cooldown reduction on teleport. Then Kennen can port every 120 seconds or so with teleport.
So with the abysaal, boots, talens, runes, Liandry's etc... That's a lot of m.Pen,
Say a champion has 100mr, void staff would take that down to 65%, and you get 60 flat m.Pen with runes, liandrys, abssal scepter, and boots. Making kennen tanky and negating a lot of enemy MR.
Of course, this is just a theory of mine.
Pair Kennen With Nami's Knockup Ult and Morgana (similar build) and this would hurt.