Wow, I had to check to make sure I hadn't written this post and forgotten! Our situation is the exact same (right down to the DS and the renewals for DH & I).
I called Monday and after a very long wait they logged in through my son's account, confirmed he had Platinum, and should have the downloads. Apparently the ability to re-assign is just a glitch - they assured me since it showed the expiry date was less than a year out that it had been activated and even if he transferred it that it wouldn't work for someone else since it's tied to his account & fingerprint (since he entered a park Sunday). As far as the downloads, they did research and called me back. They said that the problem was that the "entitlement" wasn't there for him and they'd have to open a ticket with IT to find out why. They told me I should hear back by the weekend so I will call on Friday for sure if I haven't heard from them. In the meantime, the CM was able to do a bulk download of all the pics into his account (so any pics that were already there he put into folders and downloaded into Photopass); however, I couldn't add borders or edit them or anything but could download them all onto my computer. We're AP holders so had pics in there going back nearly a year. But about 50% of the download (of hundreds of pics) were the stock photos which I then just deleted from my computer before saving the images. He did emphasize this was a one-time thing and that his new AP (son is technically a FL resident but military so lives in Boston but it was new, not a renewal) PP pics should begin on October 4 but that he was giving me all the old ones while they figured this out. I can update once I find anything out!
While on the phone for hours Monday I did ask this question since we had friends visiting Sunday as well. They also looked into this (ie the CM just didn't seem to make up an answer but went and checked on it). He told me that anything that was viewable on my son's account (the one with Platinum) he would be able to download. So if your friends link on MDE with you and click the box to allow you to see their pics then you will be able to download any for them. Just realize though that you'll either need to give them your log-in or you'll need to be the ones to add borders/edit, etc. If they edit on their account and then you download, you won't get what they did (just the original). Similarly, realize that adding a lot of friends will really bog down your account. We're local and have had lots of people visit (and took lots of pics). Now I'm on the point that there are hundreds, if not thousands, of pics on my account. (Although they say they go away after 45 days, when I go to PP in Epcot it still brings up ones from last December). Now that the window for AP holders is 365 days, there will be even more. Every time I do anything with the MB (try to get my free Chase Visa photo in Epcot, try to pull up my pre-order at BOG), it takes FOREVER to load as it has to pull up all those pics as part of the process. So while it sounds like you can do it, I'd probably limit it to good friends or as a minimum, once you've downloaded all their pics from a trip, delete them all from your account.