I'm fine with aluminum fittings in the engine bay, but all my fitting on the firewall itself will be stainless or plated steel. An engine fire thats bad enough to melt an aluminum AN fitting in the engine bay is already a total loss of the airplane, as it would take the temper out of all the aluminum structure and I would never trust it again, even if I did manage to land it safely. So melting VA-168 when its completely in the engine bay might make a bad situation a tiny bit worse. All the hoses going to that should have restrictors in place to limit flow, so you won't be dumping fuel and oil onto a fire, but you will have a some fluid leaving the hoses. Having a melted fitting in the firewall makes a bad situation catastrophic, because now I don't even have clean air to breathe while I'm attempting to land the plane thats on fire, and likely you'll start melting wiring and losing visibility as well.
The attached risk matrix can highlight what I'm talking about. A melted fitting in the engine bay is improbable or remote chance of happening, but the severity is negligible. You're already on fire and melting that fitting isn't going to do much, so the risk is low. A melted fitting in the firewall is also improbable or remote, but the severity is either critical or catastrophic, so the risk is either medium or serious. The trade-off here is you can buy more risk tolerance but it costs you weight. Up to you to decide what your personal level of risk tolerance is.