I think Dano/Petan are potentially closer value to Fowler, but not today. We still need to see them play a full season in the NHL. Petan's really impressed me since his call up at the end of last season and Dano's got a knack for scoring in those dirty areas around the net. A full year of them doing their thing and one less year of Fowler and I could see one of them being pretty fair game one for one. Today? The value just isn't established and I have no clue why the OP included a bunch of fringe NHL'rs / bottom 6 players when he said the basis was a trade for a top 6 winger.
Essentially, our top 6 winger prospects/young players Ehlers, Connor, Laine are too much value for Fowler at two years, but we don't have anything else that's one for one today on an ELC or helps their cap. Perhaps Dano/Petan + Lemieux is closest in value for Fowler today. Dano (0.925M RFA end of season), Petan (0.758M x 2 years RFA), Lemieux (0.839M x 3 years RFA). I guess the other thing one would need to know in a deal is how much cap space the Ducks need to shed to re-sign Lindholm and Rakell.