The advancement of cooperative autonomous vehicle systems depends heavily on effective coordination between multiple agents, aiming to enhance traffic efficiency, fuel economy, and road safety. Despite these potential benefits, real-world testing of such systems remains a major challenge and is essential for validating control strategies, trajectory modeling methods, and communication robustness across diverse environments. To address this need, we introduce ConvoyNext, a scalable, modular, and extensible platform tailored for the real-world evaluation of cooperative driving behaviors. We demonstrate the capabilities of ConvoyNext through a series of experiments involving convoys of autonomous vehicles navigating complex trajectories. These tests highlight the platform's robustness across heterogeneous vehicle configurations and its effectiveness in assessing convoy behavior under varying communication conditions, including intentional packet loss. Our results validate ConvoyNext as a comprehensive, open-access testbed for advancing research in cooperative autonomous vehicle systems.