Well run teams build a talent pipeline, then trade off it, keep the prospects you like best, trade veterans blocking them when they're ready, and trade the 2nd tier prospects who are blocked down the road.
You don't start trading draft picks until you're a perennial contender that expects to pick in the 20s, at that point your 1st and 2nd rd picks aren't as valuable to you as they might be in trade.
I think Briere might add an older veteran center, but he has Couts in that role. They're not going to get into the Marner sweepstakes (they don't have the money and he's too old for their timeline).
I'm not worried about the 1C or 1D issue, it's nice to have a 1C that can play 20+ minutes, but good teams are constructed more with two scoring lines a decent third line and a fourth line that's hopefully not a black hole. When you have a Michkov, you don't need a 1C next to him, he'll carry that line and elevate any center. Same if they end up with Martone instead of Hagens or Frondell. And if they go 3-4 lines deep, that compensates for a lack of a super star center.
Same with 1D, a lead dog who can play 25-30 minutes is great, but it really comes down to 2 solid pairs and a 3rd pair that won't embarrass itself for 15 minutes a night. If you have 4-5 solid D-men, they can all play 20+ and your 6th D-man can be a PP specialist who you can shelter.
More than one way to skin a cat.
The focus should be on adding good players, both for the team and as assets to make strategic moves.