> It seems both more straightforward and more effective to build recursion paths that you can trust aren't doing any intentional or unintentional caching.

I agree, but as you say, that will take quite some work and time to happen and will be costly. I was thinking of this as a possible temporary mitigation which would retain some benefits of caching. If it was made adaptive[1], it would also have the nice side-effect of being more resource intensive for those servers that attempt to use tracking.

[1] i.e. only fetch many responses if they appear to vary while doing a smaller number of "probing" requests. Continue fetching more responses for your local sample until they stop varying with some degree of confidence.