I would never voluntarily design Flexray into anything. It's not especially fast, it's conceptually convoluted, the resulting bus is brittle, and there's very few choices for silicon. I spent a flight to Germany reading a book about the bus (I was working on a project that needed to interface with it).

Traditionalists like to point to its latency guarantees, but you can do just as well with a thoughtful Ethernet implementation. And there are single pair PHYs. Others argue in favor of the multidrop topology, but I see it as a common failure point. Plus it erodes the utility of the bandwidth.

For multiple drops I like CAN a lot better.