Hey Lobo,
Harvey/Gray are definitely good targets, and are likely to outscore your current F4/5/6. The problem with shifting Dangerfield up is you are basically saying that Roughead/Pavlich/Wingard are better scoring prospects than SJ/Libba/Fyfe. The move leaves Rough/Pav/Win in your team, while Danger takes a spot that could be taken by better scorers than Rough/Pav/Win.
It comes down to 3 choices.
Choose which one of Rough/Pav/Win you are willing to sacrifice to get Harvey/Gray.
Find a way to trade in Harvey/Gray that moves Rough/Pav/Win to F7 for loopholing/back-up purposes.
Live with the fact you just can't have Harvey/Gray, unless you are happy for them to sit at M8, because even though you'd shift Dangerfield up there, it is the equivalent of having Harvey/Gray at M8.
Roughead and Pav have lowish B/E's, and Wingard has a highish one. Keep in mind that Wingard's B/E will reduce dramatically next week, when his 10 drops out of his pricing cycle. All three of those players would appear to be some sort of chance to miss games, but it would seem likely that Pav is the one most likely to get a rest, or even worse a "red vest" rest.
I think you'd better off targetting someone like Fyfe, even with the "Lyon effect" factored in, than sitting a DPP Fwd in your Mid line. You have Shenton in your Mids right now, creating the desired link, you don't need/want another on the ground.
Good luck