I agree with the simpler approach you’ve outline and comment @ygao. And the MRCM for |Contains clinical drug| already supports using MPF.
Some additional comments:
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We actually use Count of active ingredient predominately, in AMT for all products. And only use the Count of base of active ingredient for the very few concepts where it’s actually significant. For most products, the two values are the same. (This also comes back to what’s really meant by these ingredient relationships that was never actually resolved).
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@lbird2 mentions ‘Sterile water’ or ‘Sodium chloride’ as examples. I remember SI specifically objecting to things like “Sterile water” and “water for injection” last year as “not really substances”. But the reality is these already exist in a number of extensions - UK, AU, Spain, Ireland - as this is the language used in pharmacopieas.
“Saline solutions” are an interesting one because we can probably model specific strengths as products. But SNOMED CT is lacking when it comes to how to model general mixture substances… Currently “Saline IS A Chlorine compound”.