[Requirement]Timeline Activity Dependent Custom Fields

Are custom fields on Timeline Activities able to have dependencies on each other? These would be dependent custom fields on Timeline Activities, functioning as Field Dependencies do in Salesforce.

As an example, if the Type = Call, then the Subtype options would display = Strategy Session, Progress Update, etc. 
However, if the Type = Email, then the Subtype options would display = Operational Check-In, Contract Renewal, etc.

Let us know your thoughts on this.