Different strategies are needed for different objectives.  

If your objective is to change the ERP system, your strategy should be to select a system that supports your current business processes and people organization, implement fast and lowcost, and afterwards exploit the capabilities of the new system.

"...first design your new way of working and then select a system capable of supporting your ambitions."

If your objective is to change the way your organization works and you need a new (or newly configured) ERP system, your strategy should be to first design your new way of working and then select a system that will support your ambitions.

"... you should implement a strategy to maintain your achievement." 

Finally, you should implement a strategy to maintain your achievement.  If your objective is to change your people and organization and you need a new ERP system to accomplish this objective, your strategy should be to select an ERP system that will support this goal, carefully design how your people in the organization would work with the new system and then implement the organizational change and the ERP system in one go. Immediately afterwards, your strategy should be to expand the possibilities of the new system and people within the organization.

"... first design the blueprint before and then select an ERP system to support what you want to do."

If your objective is to simultaneously change your business processes, your people organization and your ERP system, your strategy should be to first design the blueprint before and then select an ERP system to support what you want to do.

Your implementation strategy should be to achieve consensus on the blueprint for the new set-up and then to implement fast, spending money to speed things up and cover for risk.

A strategy of revisiting the design of your business processes, your people organization and even your system configuration after implementation depends on having the time and people resources to do so.