I'd definitely pay for Season 3, and also a Season 4 although that seems unlikely.
As for content, I'd say Greece and Finland rallies as a minimum. I've been playing a fair bit of Rallycross recently so for completists sake I'd like to see the last two tracks from the 2018 season.
As for extra stuff, I'd love to see at least one other long stage for each rally, although given the DLC rally tracks are literally just what was in Dirt Rally I won't be holding my breath. Dynamic weather would be nice too.