Like you said signing Michaev and Kuzmenko we have a deep forward group.
Those forwards need the puck. The puck has to be pushed up the ice tape to tape quickly for them to to be successful.
Forwards can't do nothing if D can't get the puck up to them.
Klingberg brings that RHD puck mover with speed and skill with 1st unit PP ability. RHD that can walk the line on PP is one of the hardest players to get in the NHL.
Ofcourse it all depends on the contract and like you said 7 years is going to be too much. But he'll be a player for 5 years the way he skates and plays the game..