Employer Liabilities Costing needs to fetch partial costing segments dynamically from Other sources

Summary:

Our Employer Liabilities are set up as Distributed Costing against a Distribution group that has all Standard earnings and supplemental earnings. The requirement is to have the employer liabilities costing fetch segments 1, 5 and 6 from salary line, while segments 2,3 and 4 are static at element eligibility level.

We have a set up that leaves Segments 1, 5 and 6 blank and rest are populated at element eligibility and the requirement is to have segments 1, 5 and 6 populate from the salary element. This is not happening as there are multiple positions that have Costing defined and is getting overridden from there. The customer doesn't want to remove position costing for whatever reason. Is there a way to achieve this through configuration? The other option I thought was to have a custom process identify the dynamic values and load them at element entry level but Employer