I think a few different options of daily tasks added to the rotation would be really great! A few suggestions:
Get X number of coins at Y location (currently, this seems to only occur for your most progressed location, and scales upward).
Serve <specific character> N times. This happens sometimes in special events, but I think it could be great in daily quests too.
Serve X dish N times.
Earn X coins from Y dish/character.
Serve customers at each (available) location.
Earn X hearts from <specific character> - could be extra hard if it's from some of the "bad" characters.
For some unique levels, it could have things like "have both <specific character> and <specific character> on the dance floor/in the spa at the same time."
Find <specific character> on the map X times (similar to palentines, they could disappear and reappear across the game screen).
Personally I'd like to see "level up a character using hearts" removed from the daily rotation, mostly because it's sometimes prohibitively expensive and sometimes I don't have enough gems to complete the daily tasks (e.g. if the last task of the day is to level up a character twice, and my cheapest characters are 8 gems a piece to level up, I'm not going to be able to finish the daily tasks without a purchase). However, I know there are business reasons to keep this one.
Just my two cents!