Given this limitation with list fields, we use Custom Entities where we need per-project values.
For example our clients require specific terminology for Versions delivered to them. We made a custom entity called ‘Client Sub Type’ and added an entity-link field to Versions. Each project creates as many 'Client Sub Type’s as needed.
The trick is to get these entity-link fields to behave like a list, where all options are displayed
when the field is being edited. If you start by typing a dash ‘-’ then all entities for the current Project will be displayed. See example gif: