It would be nice to have possibility to define per project values of custom fields (that are List type), and also have possibility to inherit values from Project-level down to Issue-level and Timelog-level.

h2. Here is use case:

Consider having a project hierarchy that all deal with issues related to one or more Assets.
Every project has its own assets defined as Asset custom field at +Project-level+ (type List).
In order to make connection of specific issue to one or more pojects asset, custom field Asset on +Issue-level+ must be created. That field is type List and inherits only +selected+ values of custom field defined at owning project.
In order to track time that is spent on specific asset(s), Asset custom field of type List must be created at the +TimeLog-level+. That field inherits only +selected+ values of custom field defined at owning issue.

h2. How can that be done (just an idea)

The following examples are written in general manner, but in order to be apllicable for above use case, only @##ReferencedCustomFieldName##@ should be changed with @##Asset##@.

h3. Timelog-level custom field inherits possible values from parent issue

That can be done by defining special syntax that will be used in definition of Custom field values.
Here is example for custom field values defined at TimeLog-Level:

Value1
Value2
##ParentIssue##ReferencedCustomFieldName##

In this example Timelog-level custom field can have multiple values (Value1, Value2), and also inherits values from custom field named "ReferencedCustomFieldName" at parent issue (indicated by @##ParentIssue##@ indicator).

h3. Issue-level custom field inherits possible values from parent project

Here is example of custom field values at Issue-level that are referencing values at parent project:

Value3
Value4
##ParentProject##ReferencedCustomFieldName##

In this example Issue-level custom field can have multiple values (Value3, Value4), and also inherits values from custom field named "ReferencedCustomFieldName" at parent project (indicated by @##ParentProject##@ indicator).

h3. Issue-level custom field inherits possible values from parent Issue

Also you might consider the possibility to inherit values in parent-child related issues, so child issue inhertits selected values from parent issue.
Example:

Value5
Value6
##ParentIssue##ReferencedCustomFieldName##

In this example Issue-level custom field can have multiple values (Value5, Value6), and also inherits values from custom field named "ReferencedCustomFieldName" at parent issue (indicated by @##ParentIssue##@ indicator).

Note:
Above is only an example how that can be resolved. I suppose that there is a number of other ways to do that in better way.