I didn't consider the lets them have their own cookies part, but I kinda like it, however I don't really know why other than I like separations of concerns. Why do you prefer that, and what scenarios have necessitated that in the past if you don't mind me asking?
Actual reason: because there are different firms administering these settlements. You want to separate these by subdomain so that there isn't a chance that an administrator from one site hijacking into another. Unless you're proposing the government to directly call/mail affected persons (might be desirable in cases like the JnJ Talc powder case where it is clearly a retail case).