The ability to control engineering process execution is of vital importance for the success of an engineering project. Thus many studies have been focusing on capitalizing knowledge and practices of systems engineering processes. We proposed in a former work a complete solution (SysPEM: System Process Engineering Metamodel) to this problem starting from the engineering process models to process orchestration and execution control. One of the main components of this solution is a scheduling engine able to reach balance between time consumption and the respective interest of each resource. But, as we implemented our solution in the context of a real-life case study, we noticed its inability to provide high quality schedules when the available resources are severely reduced, this limitation is due to the fact that the scheduling engine is limited to using the available resources given as input as an absolute constraint. In this paper we will provide a solution to this problem through the proposition of additional resources in a cost optimization context. Our work is strongly linked to our former publications, conveniently cited in this paper, as the completion of the original solution and, as we shall see at the end of the paper, shall be considered in the context of the same case study in order to review execution results.