Yes, it sounds like a good opportunity for those that claim to be BECM refurbishers. My guess is either it's not a simple fix (high skill + expensive equipment), not profitable at the price people would be willing to pay, or few expect the supply issue to last long enough to invest in setting up a refurbishing line. If the backlog for the OEM parts starts shortening, your new business investment could be wiped out.
This thread is not focused on BECM's but repair parts in general. Toyota is having issues with wheels falling off some cars. Repair parts can be backlogged. Now we are talking about someone setting up some kind of 3rd party fix? Probably not. Legal liability at a minimum would be an issue. Could be warranty related items as well for connected parts/systems. I've seen dealers refuse to work on a car until the mods/non-oem parts are removed and replaced with OEM for example. "My engine is running rough. Well, you have someone else's manifold on it. Replace it with an OEM and then we will take a look", that sort of thing. Won't stop them from working on the radio, tail lights, etc., but the gas engine? Yup.