Been playing Adventures more recently and thinking about the 'pay' mechanism. What do you think of something like
Action -- $6
+$1
+1 Buy
Pay up to 4 Actions (Actions, not Action Cards), +$1 per Action paid.
Basically, an Action version of Diadem. It has to be worth it if there are no villages on the board, so I'm not sure of the other benefits to the card, or if it should cost $5 or $6 -- if it's too cheap, it'll get too cwazy on Champion boards, etc, if it's too expensive, well, it's a ridiculously expensive Herbalist if you have no actions remaining. Maybe paying this many actions is rather niche, and it could even cost $4.