Add an element "valueFilter" for use within DataRequirement.
http://hl7.org/fhir/metadatatypes.html#DataRequirement

valueFilter will be modeled after
http://hl7.org/fhir/R4/metadatatypes-definitions.html#DataRequirement.codeFilter
and
http://hl7.org/fhir/R4/metadatatypes-definitions.html#DataRequirement.dateFilter

Within valueFilter, define sub-elements
path, searchParam, and value[x]

Choices for value[x] would include
valueQuantity Quantity
valueString string
valueBoolean boolean
valueInteger integer
valueRange Range
valueRatio Ratio
valueSampledData SampledData

It is expected that CQL logic for eCQMs would retrieve FHIR Observation resources and then ask questions in a "where" clause about certain values of Observation.value[x].
DataRequirement now supports codeFilter for comparing Observation.valueCodeableConcept to a value set, and dateFilter for tests of .valueDateTime, .valuePeriod, and .valueDuration. The other choices for Observation.value[x] cannot be expressed in DataRequirement.