The end of Dennardian scaling in advanced technologies brought about new architectural templates to overcome the so-called utilization wall and provide Moore's Law-like performance and energy scaling in embedded SoCs. One of the most promising templates, architectural heterogeneity, is hindered by high cost due to the design space explosion and the lack of effective exploration tools. Our work provides three contributions towards a scalable and effective methodology for design space exploration in embedded MC-SoCs. First, we present the He-P2012 architecture, augmenting the state-of-art STMicroelectronics P2012 platform with heterogeneous shared-L1 coprocessors called HW processing elements (HWPE). Second, we propose a novel methodology for the semi-automatic definition and instantiation of shared-memory HWPEs from a C source, supporting both simple and structured data types. Third, we demonstrate that the integration of HWPEs can provide significant performance and energy efficiency benefits on a set of benchmarks originally developed for the homogeneous P2012, achieving up to 123x speedup on the accelerated code region (∼98 % of Amdahl's law limit) while saving 2/3 of the energy.