S/4 HANA Strategy

Hi

My customer has four ERP systems. We have kixk started our S/4HANA roadmap and are looking at various options. The existing system have norhing in common like processes or organizational structure. The client sponsor wants to keep tbe same processes in place but convert to S/4 HANA. Howver the finance user wants a single system with a possibility to do consolidation as well in a single system. What in your experience could be the path to S/4 HANA. Any guidance will be very valuable.