Classical electrochemical impedance spectroscopy (EIS) is a well-established diagnostic tool for fuel cells, enabling direct quantification of the complex impedance between an applied oscillatory current excitation and the resulting voltage response. As a possible extension, electrochemical pressure impedance spectroscopy (EPIS) was frequently mentioned, aiming to augment conventional EIS by explicitly investigating the relation between pressure dynamics at the flow-field level and the corresponding electrochemical voltage response. Since EPIS has been proposed by several authors in the past as a promising diagnostic extension, the aim of this work is to design experiments and investigate setups to gather comprehensive information about frequency-based behavior, particularly with regard to degradation-oriented modelling. Specifically, the presence of various coupling effects in the gas conditioning of a fuel cell system makes it challenging to identify fuel-cell-specific spectral features while minimizing the influence of balance-of-plant components. For this reason, a feedforward decoupling control scheme is implemented on a fuel cell testbed that accounts for the strongly coupled and nonlinear relationships between pressure and the supply air for the fuel cell cathode. Beyond improved decoupling performance, this approach has the potential to significantly mitigate the impact of balance-of-plant components. In this context, key hypotheses regarding EPIS are investigated using distinct single-cell configurations across different life-cycle states to examine characteristic effects. A structured design-of-experiments strategy for the testbed and control approach is proposed to explore the observability of physical processes through reduced pressure–voltage impedance coupling. The analysis focuses on frequency-domain sensitivity as well as resistive and capacitive effects across different fuel cell degradation states, with attention to applicability limits and implications for experimental design.