Converting External Attribute Mapping to Standard IBA on WTPart without data corruption (Windchill 1

I am using Windchill PDMLink Release 13.0 and Datecode with CPS 13.0.0.0 We need to modify our data model regarding a specific soft attribute on wt.part.WTPart. Currently, we have a soft attribute with internal name Code defined on the WTPart. However, it is configured using External Attribute Mapping pointing to the Master: masterReference^wt.part.WTPartMaster~Code. Because the attribute is mapped to the Master, it behaves as a mutable global value. When a user modifies this attribute, it updates across all historical iterations and baselines. This breaks our baseline integrity because we cannot retrieve or freeze the historical state of PreferenceCode at the time the baseline was captured. We want to convert PreferenceCode into a standard, unmapped soft attribute (IBA) residing directly on WTPart (iteration level), so that each iteration freezes its own value and standard Windchill Baselines can capture it out-of-the-box. To avoid breaking a massive amount of existing customization, source code, validators, and workflows, we MUST retain the exact same Internal Name (PreferenceCode). What is suggested way of solving this kind of change in Windchill?