Here is a thought experiment that I think could be worthwhile. For theists, the question is roughly as follows. What is the nearest possible world (the one maximally closest to our actual world) wherein your god(s) does not exist? This question is of course specific to your particular theistic conception, whatever it happens to be. So, let's say you believe that there exists some god(s) with properties x,y,z....; then what is the nearest possible world wherein no such entity(ies) exists? What does it look like relative to the actual world?
For atheists, the question could be roughly as follows. What is the nearest possible world wherein god(s) does exist; what does it look like relative to the actual world? However, this question is too unconstrained because it is not specific to any particular god-conception. Perhaps we would need to constrain the question further to make it interesting.
To lead by example, I will play first. As an atheist, I lack belief that any god(s) exists. What do I think the nearest possible world wherein god(s) do exist looks like? Again, this presumably could depend on what god-conceptions are at issue. If, for example, the god at issue would be one wholly unconcerned with human affairs, then presumably the answer is that the nearest possible world wherein such an entity exists is just an exact replica of our actual world. If, on the other hand for example, the god at issue is one intensely interested in human affairs, then presumably the nearest possible world could be quite different from the actual one. However, let's consider a specific example of a somewhat traditional conception of 'god' as a personal creator, interested in human affairs, and having properties including omnipotence, omniscience, moral perfection, etc. Personally I think an evidential problem of evil shows that we ought to expect the world to be quite different from what it is actually is, were such an entity to exist. However, I also think that logical
formulations of the problem of evil fail: that is to say, I think arguments that purport to show that the evils that exist in the actual world are logically inconsistent
with the existence of such an entity, are unsound. (For instance, I think it is broadly logically possible that we are simply radically confused in our valuation of putative evils in such arguments and that it is broadly possible that they are necessary for some greater good.) Since I think it is broadly logically possible
(despite how evidentially improbable I think it is) that such an entity exists even given all these putative evils; then I would have to conclude at least on the basis of only these considerations that the nearest possible world wherein such an entity exists is still just an exact replica of the actual one. Further, I know of no arguments that show that the existence of such an entity is logically incompatible with our actual world. Further, I know of no argument that shows such an entity is logically impossible simpliciter (although I think the omni- properties involved are quite difficult to coherently formulate). So I would venture that the nearest possible world wherein such an entity exists is just a duplicate of the actual world.
This question may be more interesting for theists rather than atheists.