Currently, dynamic custom fields are only possible via Scriptrunner, but allowing users to create certain dynamic custom fields up to an extent would help a lot of users as not all organizations are able to afford an extra addon for a singular purpose.

Allowing custom fields to set a default value based upon another custom field would be a nice addition to workflows and would eliminate the need for those particular niche cases where the creation of this could greatly improve the workflow without the need for a complex/advanced addon for just that purpose.