Quick update: responseProcessingMode landed in https://github.com/apache/jmeter/pull/6708, built on Joerek van Gaalen's #6389. I'm happy with how it turned out.
One thing worth flagging for the list: to let old .jmx files pick up the new setting automatically when they load, I added a small "upgrade on load" mechanism. JMeter already rewrites old property and class names on load through NameUpdater, but it can only rename them, not change a stored value. The new TestElementUpgrader SPI fills that gap: services are discovered via ServiceLoader and run by SaveService after a plan loads, so a module can upgrade its own legacy settings to the current form. responseProcessingMode is its first user. It's bundled in the PR so you can see it in context, but I'll split it into its own PR, since it's a general mechanism other migrations could reuse. Vladimir
