The thing I was always wondering about brain simulations is how to determine what level of detail is enough. What if neurons evolved to take advantage of some funny quantum phenomena that we may not even know about yet, and without this the simulation won't work? For this reason I would think that getting a simple brain simulation to work would at least help enumerate the physics most involved in their function.

Now maybe there is some extra physics that comes into play at scale (like some quantum-computery effect with human-size brains that induces conciousness) but maybe this would be detectable as small discrepancies in the small simulations (especially as they progress in size to e.g. mice).