The next version of CRM Core is going to unlock the contact_name field and allow users to alter it's settings. This introduces the possibility that users can delete this field, which is a problem because there are things in CRM Core that depend on having a contact_name field of field type == 'name' in order to work.
This issue is for tracking problems that might arise if the contact_name field is deleted and replaced with something other than a name field.
1) The crm-core/contact view will break if contact_name is not a name field. The view will not be able to apply filters for sorting and this can lead to warnings and errors when it is displayed.
2) Autocomplete fields will break if contact_name is not a name field. No results will be returned.
3) CRM Core User Sync will break if contact_name is not a name field. The entity field query logic used to identify contact records based on keyword searches will generate errors if they are being used to search something besides a name field.
This seems like too short a list. If you are running into issues with changing the name field to some other sort of field, please mention them here.