Rules and Errata

Race Dorsey:
"There should be a rule that rallied supporters are AP specific and cannot be rallied into a different AP. Much like Loot has "When setting up any scenario in that adventure path," verbiage.
Say you are playing Sanctioned Curse, you cannot then use those rallied Curse supporters while playing scenarios from season 6. Only supporters rallied during season 6 would be eligible to use during season 6 and same would need to apply to Curse."
John Francis:
"It looks as though Season 6 is already assuming that supporters were AP specific. Note that the storybooks contain explicit directions for proxying the Season 6 supporters with named Core+Curse supporters; that would be impossible if some character in the party had access to one or more of the named supporters.
"Another reason to think supporters must be AP-specific:
If a character who has earned access to one or more supporters in Year of Rotting Ruin plays in a scenario in Curse of the Crimson Throne there's no guarantee that the game box would even contain those supporters.
(And, presumably, the same sort of thing will happen once a new Adventure Path is released - you can't depend on the game box containing anything other than the cards called for in the Adventure Path you are playing)"
Race:
"Not to mention season 6-2 has supporters that are proxied with other supporters from CotC.
It's fairly clear to me that this is nothing but a rules gap and there is 0% intention that supporters were intended to be used cross-AP's."