Although the distinction would be subjective, it might be worth splitting the list into two sections: mechanics that feel substantially new in play, and mechanics that are new in more subtle ways.
For example, Patron's when-reveal trigger feels like a much bigger deal than Exeriment's trick of gaining a second without that then gaining a third.
(If we're being pedantic, though, I'll note that Caravan Guard is a (non-Treasure) Action you can play in the Buy phase. Albeit not your own Buy phase. (-8 )