Answer

That is definitely a meaningful question, but it is a different question. The original question is meant to prove that there is no God, or that He is not omnipotent. The questioner is trying to corner the believer and show him that his position leads to a contradiction. But your question does not do that. Even if I accept that He can turn Himself into non-omnipotent, there is no contradiction in that, and therefore it is not a challenge to His existence or His omnipotence. Conclusion: this is a different question from the one I was talking about.
Of course, one can also engage in some casuistry about this. The question is whether His omnipotence is an essential part of His definition; if so, then when He turns Himself into non-omnipotent, that would no longer be Him. Just as a person cannot turn himself into a mouse, because when he is a mouse, that will not be him. He simply destroyed himself and created a mouse.