1) Very high-fidelity codes which you’re describing, accurate at the molecular (atomic?) scale are typically never usable in any meaningful sense for macroscopic scenarios. This is usually because they’re either too computationally expensive, taking too long to run even on huge supercomputers, or because we actually don’t know how to bridge the gap between the small and large-scale physics behavior.
2) It’s unclear what you mean by “incredibly accurate”. Different fields have different definitions of what accurate means (as well as different kinds of physics they’re trying to take into account) so your ultra-accurate simulator in one domain might be very off in another. From reading your comments it seems you’re most interested in materials science. That’s not my direct field of expertise but if they’re anything like every other field of science/engineering, there is a very strong division in the field with regards to what kinds of simulations are used where.
3) This is something people usually don’t think about, but stuff like materials research is protected not just by proprietary laws but actual government export control laws. So not only will such a distributed system be looked at with raised eyebrows by corporations, but the US government might move in to shut it down if there’s suspicion that the distributed information is getting to nodes managed by foreign nationals.
In short, there are a plethora of issues related to the scope and objective of what you’re proposing. It would require a Herculean amount of effort for an unclear payoff, unfortunately.