I was actually a little bit surprised at how little effort people have put into the problem - particularly Lloyd Chambers, who when confronted with the existence of Adobe Flat Field (which is how I got onto this), basically just griped that it didn't work with ACR and that Leica should have designed its system better. This is not uncharacteristic of the professional reviewer ranks; there does not seem to be a lot of investment in solutions.* And in this instance, I wonder about professional reviewers' view of what is practical in real life, too - since Flat Field exports to a DNG, you can still pull the resulting file into ACR. Even if you wanted to control illumination falloff in ACR (which makes no sense to be since ACR and Lightroom are similar if not identical in these controls), Adobe Flat Field lets you correct only the color shift if you want.
Dante
*That's not surprising; in a world where people get free loaners to the point where the FTC requires disclosures, the emphasis is often on throughput, getting the scoop, and providing enough material of wide interest to justify the subscription charges. People who buy their own equipment have more time, less pressure, and additional incentives to learn how to make things work. In this case, the total time investment to fix this problem was actually about two hours; writing it up took half an hour.