Suppose we discover our universe is a simulation. This would imply that the universe is Turing-computable. Would there not therefore exist a "Grand Unified Theory" that simply described, with absolute precision, the operation of the simulator? Or would it be impossible to produce such a specification?
Then all you have to do is demonstrate that we live in such a universe, and all the philosophers can retire because we've found the ultimate answer to the ultimate question.
I think we all know exactly what the Gödel number for our universe would be...
Rudy Rucker had some interesting conversations with Gödel about a deterministic universe in which (because time is illusory) backward time travel exists: http://www.rudyrucker.com/blog/2012/08/01/memories-of-kurt-g...
The author stresses that all of reality is mathematical in structure, but this is at odds with the fact that all mathematical systems containing self-reference are necessarily incomplete. Physics is a self-referential system.
If the structure of the universe is mathematical, it is probably a very different math than humans are used to. Insert your favorite flavor of metaphysics here!