Look into the filter like the 5" media hepa type. An example is the "April Air 2200 or 2400". This would have to be installed at the indoor system, and the filter changed once a year.
There is one that fits into the wall or ceiling as well.

You can also get a return filter grill in a 2", and use one 2" filter or two 1" filters.
I have systems I installed 20 years ago, and with the 5" media filter, there isn't even any dust on the inside of the air handler, needless to say- the indoor coil and blower has never needed cleaning.

Thanks. So it does sound like it is feasible. What about a hinged return grill cover? Any place I can pick this up online? What is the real name?

OK, I found the hinged return grille cover at Atlanta Supply. They called it a Filter Return Grille. I have about 6.5" of clearance behind the grille so I think I'll look into the deep filter (4"). I paid $22 each so I thought that was worth it versus trucking up to the attic every 2 months.