What kind of coding gymnastics will they have to do so that DD is not affected by these specific keystones?
Exactly the same kind that has existed since closed beta to prevent the additional life monsters get from party size affecting detonate dead.
To be specific, Detonate Dead already uses "intermediary maximum life", which is a separate stat calculated from the base and applying most but not all modifiers. Further modifiers are applied to that stat to get actual max life used for the amount of life stuff has.