Ok, so let's say they both want to go. 
What could we expect to get?
When Roos was coach at Sydney they wanted Martin badly. Pick 2 from the Dees? I don't think he would slip to them in the PSD with the GWS lurking. 
The GWS? Pick 10 and Adams. No chance of getting pick 1 from them. Maybe even Tyson and Adams? 
Conca to West Coast? Pick 6 or player like Scott Selwood or Andrew Gaff. 
Best case for me, besides them both staying, would be
In: Pick 2, Scott Selwood
Out: Conca, Martin
Pick 2 used on Boyd  

 and pick ~11 on Taylor Adams
Final ins: Adams, Selwood and Boyd
We lose two mids but gain two ready made replacements and get the gun KPF of the draft.