Nothing gets me as excited as a lowly footsoldier in a company as when the c-suite decide to spend $100mil doing a custom install of a big name software stack that will "totally change the way we work and at the same time be fully customised to the way we work here".
You do not modify SAP to fit your company, you modify your company to fit the SAP model.
You can try it the other way, but the project will always cost millions and it will eventually fail. It always has and it always will.