New S/4 HANA Service is simplified solution, but it has come up with lots of limitations, down the line of 5 years do not have many improvements. Even basic features like warranty check not works properly.

In-Inhouse request (REPA) it reads warranty dates from equipment, whereas in service request (SRVR) it reads warranty start date and master warranty. If same equipment used in two process (In-house and field service) logic is failed.

New In-House repair is not a good functionality, it did not have output, attachment, email, categorization, activity, task, SLA functionality, as like service request. It should be exact as similar as service request (SRVR) and actions should be add for logistic integration. 

No determination of Service organization in order, system should determine it service organization as like service team.

Repair quotation and repair order do not have warranty fields.

Currently repair quotation/order supports one equipment only, no multiple equipment's

In reference object list must have warranty field, it is useful when there are multiple technical objects, so against each object warranty details can be viewed.

Service request do not have vendor/manufacturer master warranty field.

Service request do not have contract determination functionality.

There is no field for company code, planning plant in request/order/confirmation, customer not able to differentiate documents based on this important fields.

Categorization schema is not much powerful, as like quality catalogs, SAP should add functionality of use of Quality catalogs as like notification, so customer can use categorization or quality catalogs. 

No integration of In-House repair with QM to trigger QM notification.

Goods issue through transaction MIGO or FIORI app Post Goods Movement, not reflect back in service order transaction history. Further control should be in place that system should not post again additional material consumption document from confirmation (backflush)

For service to SD sales order integration flexibility should be there to mention different sales document types with any number range. 

When confirmation canceled it did not reset service order item statuses, currently statuses need to be reset manually. 

S/4 Service do not come with any Service resource planning functionality, SAP strategy is for resource planning customer to have SAP FSM, but what if customer do not have FSM and do not want to go for SAP FSM just for resource planning?.  There should be basic service resource planning functionality.

Advance shipment introduced with traditional approach same as SAP CS, looks like lift and shift from CS to S/4 Service, no flexibility to create sales order for customer and technician. 

Currently One Service order = One Sales order which is poor design. There is no provision for specify sales document type in configuration.

From search service order apps there must be option of create follow up documents, currently user have to go in each transaction detail and have to create follow up.

Maintenance service order (MSO) is again not good solution, SAP recommending adopt new S/4 Service module and again introduced old concept, where MSO1 will replicate in PM order, again work with operation (task list), component and resource related billing (This introduced for customer who use heavy use of operations). In old CS resource related billing based on DIP is complex one, same again have to use, if customer choose to go with Service and MSO option.

Such limitations are posing challenges in projects, customer who are using SAP ECC CS for them it is more challenging because customer never want to lose existing functionalities.

Better, SAP can improve before it's too late. 

Thanks