Unfortunately, the HVAC system has many connections at the unit as well as ducts the run throughout your home. Changing the filter only has to be done maybe twice a year. Getting to the unit in the crawl space is a small price to pay for perfect temperatures all year long.

You could put the filters in the returns instead of the units. If you have one or two big returns in your home. You should contact a HVAC contractor and get their opinion on it.