I reckon it will end up being something complicated that gives GWS a 'win' (e.g. a higher first rounder or sufficient aggregation of points to be somewhere between late first rounder & mid second rounder) but also Freo a win (McCarthy plus something, e.g. keep a first rounder or get two first rounders). I suspect that GWS would consider a 3rd round value as insufficient. GWS probably don't need more picks in 2016, but might still elect to take a trade in this year's points/picks with Freo, and trade another 2016 pick for a 2017 pick (Melbourne, Geelong & Collingwood might be interested).
So, yes, even though points-wise your option 1 = option 4, I'd see option 1 as still possible and perhaps even more likely. Option 2 is equivalent to pick 22, option 3 equivalent to pick 24 so they both fit my thinking - GWS might try to perhaps also squeeze Freo's 4th round pick to get it closer to a first round value. With future trading and GWS's several first & second round 2016 picks, there's plenty of options to make a trade happen. And I reckon it will - I'm assuming neither side sees any value in McCarthy sitting out another season.
Personally, I would see option 3 attractive if I was GWS list manager. (Although I think the Collingwood pick might be a touch lower at 6 or 7.) Freo can say it's only giving up effectively a 3rd round pick, while GWS say it's getting an improved 1st round pick. Actual value in the 2nd round, which is probably not an unreasonable mid-ground. Practically, if Freo only dropped from 3 to 5 (or even 6 or 7), you'll still get a highly rated midfielder, and get a forward in McCarthy - you'd call that a win. And GWS get a higher pick - if Macreadie gets called high then the points cover him, or even see if Marshall is there to pick. (Would depend on how Marshall's being rated near draft time, and sense of what Bombers & Lions are wanting in the draft.)
Yep there would likely be a bunch of lower draft picks exchanged to provide points. I think this new system provides greater flexibility and the idea of losing a trade doesn't necessarily need to occur in this situation.
Many teams can use academy picks to barter in their favour, but in reality it also favours the team bidding.
A deal will get done.
90% saying give us your first and those saying we'll only give you our 3rd probably have no idea about the intricacies that make up the points system.