  A considerable amount of research and engineering went into designing proxy
applications, which represent common high-performance computing workloads, to
co-design and evaluate the current generation of supercomputers, e.g., RIKEN's
Supercomputer Fugaku, ANL's Aurora, or ORNL's Frontier. This process was
necessary to standardize the procurement while avoiding duplicated effort at
each HPC center to develop their own benchmarks. Unfortunately, proxy
applications force HPC centers and providers (vendors) into a an undesirable
state of rigidity, in contrast to the fast-moving trends of current technology
and future heterogeneity. To accommodate an extremely-heterogeneous future, we
have to reconsider how to co-design supercomputers during the next decade, and
avoid repeating the past mistakes. This position paper outlines the current
state-of-the-art in system co-design, challenges encountered over the past
years, and a proposed plan to move forward.
