If Ducks were to sign Marner, I would roll 4 scoring lines next season. I often notice our players are out of fresh legs often, and if we intend to play some of our top offensive players on the PK, I think this strategy would suit us well, even under Cronin. It'd also create easier matchups for some scorers at all times.
Nesterenko - McTavish - Marner
Cutter - Leo - Colangelo
Killorn - Zegras - Sennecke
Vatrano - Strome - Terry
Roll them fairly evenly, giving more time for whichever line is hot in any particular game. Load up the PK and PP so guys who need/thrive with more minutes get them, and ease in guys like Sennecke there.
At some point upgrading Nesterenko would be ideal but I think he can suit a Kunitz type role helping M&M and potting a few garbage goals.
Try to employ an attack, attack, attack mentality which we have seen a little bit more of lately vs early on in the season - but we see them running out of gas, also.