So, get a prescription for the dose of med that will increase to your desired dosage when you have your grapefruit or juice. Win-win.
You misunderstood the effect of inhibiting P450. If the intended "net" dose of a medication is 50 mg, the actual dose provided will be 100 mg assuming the P450 will degrade half of the dosage provided. If you consume grapefruit juice, the P450 is inactivated. The 100 mg dose arrives undegraded. You have just overdosed by a factor of 2x.