Big results typically have a lot of implications and connect different fields together. This sounds like something that could be measured objectively. You can

Big results typically have a lot of implications and connect different fields together. This sounds like something that could be measured objectively. You can also try reproving old theorems with newly discovered methods. So if suddenly you can reprove results in different fields with a new method, that sounds like something that might be big and should be investigated by humans. Of course, what I wrote above will miss subtle things, but there is a place for a system which can just brute force it's way through mathematics.