Sure, I can understand if your goal is not to deliver end services cost-effectively but rather to fully utilize your existing hardware. My suggestion is that you can do both -- having a stable and performant platform for daily services (e.g., Plex and VDI) frees you up to experiment with ProxMox on the blades, with the flexibility to shift workload over as you gain confidence, and the safety of being able to fallback to a known-good solution.