It really surprises me to hear that it takes 9 months for the body to clear gluten. Why is that? Do you have a description of the process of clearing gluten that you could link to? Because I really don't understand how a substance could hide out in your colon for 9 months.
But if that is the case, then eliminating gluten is way too slow to be relied on as a treatment for childhood asthma. You simply can't wait 9 months to see if eliminating gluten might make the child better - breathing is too important and the wait is too dangerous. There are reliable treatments for asthma that take effect much faster and don't require dietary restrictions. I guess you could experiment with gluten once the child's asthma is under control. So you could do 9 months of meds while eliminating gluten, take the kid off the meds and see if your dc has an attack or comes down with pneumonia. That doesn't sound like fun to me, but I suppose you could try.