If I understand correctly, what this boils down to is that for any given hit, the effective armor value is the weighted average of the different armor types, with the weighting provided by the ratio of damage types in the attack.
It looks like it will meet its goals, but I’m a bit concerned about explaining how it works to contributors or players, because armor value no longer means something straightforward like, “absorbs x damage of type y”, it now requires explaining this weighting scheme.