Babcock said he likes to put Brown over Nylander on Matthews line so he can play against any matchups. I very much doubt Brown would play on a sheltered line and the fact Marner is still on the sheltered offensive line probably proves Babcock doesn't think he should be playing with Kadri who will be centering the shutdown line no matter what.
My belief is that Marner hasn't been on Kadri's wing because Babcock wanted to spread the wealth. Marner's on Bozak's line imo to help that line out defensively while Nylander hasn't been on Bozak's line because he still needs work defensively.
Either way, I like duos of Matthews-Nylander, Kadri-Marner long-term if Willy doesn't go to center.
xxx - Matthews - Nylander
xxx - Kadri - Marner
xxx - xxx - Kapanen
xxx - Gauthier - xxx
That type of 'core' kept consistent and filled over the years with Bracco, Timashov, Johnson, Brown, Leivo, Hyman, Grundstrom, Korkshov, Soshnikov, Rychel, etc should be the layout.