Is there any reason for why most of these panels should only be visible for some engines? Feels like they should not care about the engine. Maybe I nicer fix is to the COMPAT_ENGINES attribute from the panels that don't need it. I did something similar here: rB16a04dccd556d2969e0.

Thanks. I'll take a look. Looks like that we don't really need many of those flags. But that's how blender's existing scripts are done....