Randomized bonus safe days

I’m playing a mobile card game called Eternal and one of the gimmicks is that your reward treasure chests have a 10% chance to “upgrade” to the next tier. Of course this doesn’t actually affect Eternal’s bottom line since it is accounted for (see also Expectorant), but it feels awesome. People (including me) go nuts over this system and even make reddit posts about it.

Would anyone find a similar system exciting for Beeminder? I know that the “fixed bright line” and “no carrot” philosophies are dominant, but sometimes it would really nice to just get a bit of a break from certain goals. Sometimes the 100% deterministic, linear safe days system feels like a drag.