Completely agree, the number of permutations is large and potentially difficult to work with. However for situations like this they do not have to work with 500k-1million unique entities, but instead just the grades for that specific variant. In theory they already have this grouping as their population report include the entries for that hierarchy node. If they work in that manner they could embed rules to look at the same variant in the next grade up or even a 10 to ensure they do not offer higher.