Attached above is the text of a cr2 where morphs are applied cumulatively via one dial, as in scenario 1 in my previous post. The morphs are expressed via the "Morph_Master" dial in the BODY actor.

Each morph is slaved to the Morph_Master valueParm channel in the normal way, and has it's limits forced between 0 and 1. In addition, the trick here is to slave each morph channel to another valueParm channel in the BODY named "One", the value, initValue, min and max of this channel are all set to a value of 1.0. The 'deltaAddDelta' ratio for each morph channel slaved to "One" is negative, and starting at zero for  Morph-01, incremented by one for each successive morph. So Morph-01 uses 'deltaAddDelta -0.0', Morph-02 uses 'deltaAddDelta -1.0', Morph-03 uses 'deltaAddDelta -2.0', etc.

It's as simple as that, the slaving to the "One" channel holds back the expression of the morph until the master dial reaches the desired value, and forcing the limits of the morphs to between 1 and 0 ensures that the morphs don't go outside the desired range.