I think that would be a question for your doctor.

We need to remember that when it comes to medications and supplements, more is not necessarily better. At worst, we are setting up for an overdose or increased side effects. At best, we are flushing money down the toilet because our body (hopefully) eliminates the excess.)

By doing adding oral NAC to the inhaled acetylcysteine, you would almost surely be exceeding the recommended daily dosage, which is 600-1800 mg per day.
Too much NAC can cause bronchsopasms, bleeding, issues with blood sugar, nausea and vomiting.

Here is the Mayo Clinic guidance on its use in a nebulizer:
https://www.mayoclinic.org/drugs-supplements/acetylcysteine-inhalation-route/proper-use/drg-20061456
I under stand wanting to do everything possible to beat back MAC, but sometimes we just need to be patient.