Perhaps for double the pizza price (1 month membership pizza price divided by 30x2) A player can purchase an individual day of the card hunter club rewards? This allows more player options and gives an incentive for players that want to be in the club but don't want days to go to waste. It would also serve to allow players to sample the club early on to see how much it does or does not appeal to them. Just an idea.
I like this idea a lot. I'd also go a bit further and incorporate a week's (7 x 24). Largely for the playerbase with busy lives and hectic schedules interspersed with short vacation periods. Also, I'd re-categorize as Card Hunter Daylong/Weeklong Boosts and such. Club refers to the more committed players while Boosts are for that friend who's pulled in for a day's/week's worth of tabletop gaming.
I think for it to work the people of Blue Manchu this could bite them in the back pocket, unless the Daylong or Weeklong Boosts are a bite more expensive. Its now $10 a month so they would have to make the Daylong say $1 and the Weeklong say $2.5, that way people can try out the members club at a good price. This would only give them the Bonus Chests, as there is already an option to by $5 of Pizza Slices and you need at lest $10 to get the full Monthly Club Bonus. And you can just buy Chests with the Pizza Slices anyway, Maybe I'm over thinking it.