I had this idea while going to the bathroom. That rarely happens. Usually, I get an idea and I flesh it out in the bathroom (most often the shower, not the toilet).
The idea is a world where the gods are active. And by active, I mean they issue proclamations and change the very laws of existence on a weekly or monthly or yearly basis.
I just woke up a little while ago so my memory has not fully booted but I do not remember a campaign setting where the gods are as explicitly active as this. Even in a setting like Forgotten Realms, the gods are mostly active behind the scenes in games (they are main characters in books but not often in games, unless the PCs are gods). And the few other instances I remember of active gods in RPGs usually sequesters them away as highly secretive or isolated.
While the campaign does not necessarily have to go this way, one easily derived storyline is to increase the capriciousness of the gods and the PCs must do the impossible to stop them - deicide.
In a less us-vs-them campaign, the PCs would have the option to directly petition their god to change physical laws to their benefit. In this case, there would have to be a limit on the power of the gods to maintain balance.