I would like a GPT capable of making significant advances in string theory. It is extremely hypothetical by nature, so I think it should be a good fit for a very strong scientific GPT to check many different hypotheses (e.g. supersymmetric theories), assess their likelihood, and maybe even come up with new ideas that have value for the scientific community.

"With a budget of €7.5 billion, the LHC is one of the most expensive scientific instruments[1] ever built" - Wikipedia

Perhaps we should invest the next 7.5 billion in an exceptionally large GPT model.