Can a constrained supply plan suggest alternate work definitions based on material constraints?

Summary:

Can a constrained supply plan suggest alternate work definitions based on material constraints?

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I have defined a Constrained Supply Plan. Further, I am using Work Definition to model combinations of items that will get backflushed upon production completion. For e.g. if a component item in the BOM has got two substitutes, we are going to define three work definitions. In summary, we are using Work Definition as a proxy for component item substitution. 

I have a basic question. In a constrained plan, can the supply plan suggests an alternate work definition looking at the material constraints (e.g. use substitute item when there is no sufficient inventory of the main item), or does the constrained supply plan always suggests work definitions looking at resource constraint and trying to level production load.