Enhancing OT Network Security with a 2.5 DMZ

In our OT network, we're considering adding a Level 2.5 DMZ to bolster security. This would serve as an additional layer of protection between the control systems (Level 2) and the enterprise network ...
UTM 9 software as ProtonVPN client

This question hasn't been asked in 7 years. Has anyone gotten this to work. Essentially, I'd like Proton to be the parent proxy for the UTM. Thanks!