Yes Boqvist will be too young. Maybe even Dahlin will not be ready just yet.
Hedman - Lindholm
Ekholm - Karlsson
OEL - Klingberg
No idea why you have Hedman with Karlsson, they are both offensive and should have someone more with a defense style playing with them.
It depends on what other players are available, if those would be only 2 elite d-men, then yes I would agree with you that you should not play them togeheter and instead spread out the firepower to get the most out of them. But if you can haver 6 elite offensive d-men, then why not?
Plus i think they could work good togeheter, they actually did play togeheter in wjc 20 back in the days and did that well. Hedman has more strength while Karlsson has more puck-skills.
Plus I want our best players to get the most ice-time. It feels weird if Ekholm and Lindholm get the same amount of ice-time as Karlsson and Hedman and more than Klingberg?
I think Dahlin will have surpass players like Lindholm and Ekholm by 2020, Lindholm has not really developed alot since he enter the league. Pretty disappointed at his devolopment, but he still a really good player.
Today I would have
Hedman - Karlsson (about 25min)
OEL - Klingberg (about 20min)
Ekholm - Lindholm (about 15min)
2020
Hedman - Karlsson (23min)
Dahlin - Klingberg (22min)
OEL - Ekholm/Lindholm (about 15min)
Then there are jokers like, R Andersson, Klefbom, Liljegren, A Larsson etc.
I agree it is probably little to early for players like Boqvist, espically consider he is a small player.