In D365 SCM, Item substitution functionality allows Master planning to substitute a component or ingredient item on a production order. When you set up item substitution, you assign BOM or Formula lines to a specific Plan group. An item can be substituted for a different item with the same Plan group. Items within the same Plan group are assigned a priority, and the highest priority item is the item that is normally consumed.

When Master planning runs, it uses the highest priority item if it's available. If the highest priority item isn't available, Master planning looks for the next highest priority item with available inventory. If no substitute items are available, Master planning creates a planned order for the highest priority item.

I believe a relatively simply change would allow Plan group functionality to support Item supersession.

Item supersession is a scenario where a component item or ingredient is permanently superseded by a different item. In Item supersession scenarios, it is a common requirement to consume all inventory of the 'old' item before switching to the 'new' item.

If Plan group logic supported the following behaviour, it would be possible for Plan groups to support Item supersession scenarios:

When Master planning runs, it uses the highest priority item if it's available. If the highest priority item isn't available, Master planning looks for the next highest priority item with available inventory. If no substitute items are available, Master planning creates a planned order for the lowest priority item.

If Plan groups supported this logic, the 'old' item could be configured as the highest priority item, and the 'new' item could be configured as the lowest priority. This logic would also support supersession chains.... where ItemA is replaced by ItemB is replaced by ItemC etc.

Later, when inventory of the 'old' item is exhausted, a manual task for the production planners could be to update the BOMs/Formulas to remove lines for the 'old' item, and remove the Plan group settings if appropriate.

It is particularly important that this idea be addressed by Microsoft, because the relevant logic sits inside Planning Optimisation, and cannot be changed by Partners or End Users.