The only potential problem is Lucic and Sekera contracts in 4 years. That's something to worry about then.
Yep, that gives breathing space, plenty of time to get ready.
With Subban trade Sekera-Subban top pairing would have had a 14.5M cap hit, while the bottom4 would have needed a lot of work to make it a contending level.
Bottom6 with Subban trade would have needed a lot of work, pretty much a new 3rd line and McDavid re-signing is waiting in 2 years.
That just seems like creating a huge cap problem into near future.
With Larsson trade the forward group has the players to become a contender in 1-2 years with (potential) forward core players being between 18-28y, potential to build a longterm contender.
Lucic-McDavid
RNH-Eberle/Pulju
Dra- Pulju/Eberle
looks scary
and Klefbom, Larsson signed at a bit over 8M longterm compined, both just 23y, great fit age wise with the forward core and good core to build around a longterm plan, then Sekera at 5.5M signed longterm, defense needs 1 player to make it a contender.
So to me the lineup looks better balanced, instead of having ton of work to do in both groups Chia can focus on defense alone while Klefbom&Larsson give him a better situation to work on improving it.
Every successfull team needs steal contracts in their lineup, quality ELC players providing value, Subban trade would have taken those away.
I may be completely wrong but this is how I see it right now. I was going by Dra, Pulju, Klef for Subban.