Similar to Harvest Moon, and Story of Seasons, I would like it if we could have an affection system where caring for and petting your animals everyday would fill up a heart meter. You gain a heart for every so many points of caring for your animal.

It would be a great way to reward us for taking good of our animals. However since the game is always online, I don't think you should lose hearts. Earning those hearts however would be a great way to earn extra rewards from each animal.