How hard is it to convert a suburban theater to a drive-in?
Biggest question mark is whether you can move the projectors outdoors. Any reason you can't set up the projector under a car canopy?
After that, the limiting factor is parking space. And most of these theaters in the 'burbs have huge parking lots. Realign parking spaces with cones to aim cars towards the theater façade, from which you can hang a projection cloth. Transmit audio to cars with a weak FM signal. This would require a small upfront investment, some local permits & shifting the schedule to later at night.
The main thing is that they can open up the lobby to sell concessions. There's still a risk of viral transmission but nowhere near what it is when sitting in a mass gathering with shared air for 90 minutes.