Tldr; Allow FlexMixes to be selected in Scene Safe settings, to prevent overwriting when loading a scene.
We run a StudioLive Series III in a House of Woship set up, with FlexMix setups for monitors, subwoofers, cry-room, assistive hearing headphones and web streaming. FlexMixes are either Pre-Fade for monitors, or Matrix mixes for cry-room, headphones, etc.
We use scenes to save service-to-service mixes for our bands, allowing volunteers to quickly load a previous week/band's mix and get working quickly. This process works for our environment.
It would be useful to Scene Safe selected mixes to prevent modifications to the subwoofers, cry-room, headphones, etc from being overwritten by a volunteer whilst loading a scene with a previous week's mix.
For our needs, course selection of FlexMixes to be safed would suffice, however other's many find finer grain scene safe controls useful in the future.