The new design for view layer dynamic overrides will likely remove scene.layer_properties where a lot of Eevee settings are stored now. Most likely we can store settings in scene.render instead, but this depends on the dynamic overrides design which is unclear still.
If we have to move settings, we can at the same time make sure the settings are shared with Cycles since we are moving them anyway. Some things that could be shared:
- Lights without nodes, Eevee does not support light nodes currently
- Light intensity differences
- Material, world without nodes?
- Depth of field
- Motion blur
- Film transparency
- Color management settings on image texture node and image datablock
- .. ?
The shared settings would be ones that affect the look, and not render quality / sampling settings. We will need version patching for backwards compatibility for Cycles, and maybe Eevee too.