I want to configure and write an EffectMaterialContent, using an effect and parameters that I get from somewhere else.
I thought this would be simple -- just create an EffectMaterialContent, set the Effect to a reference to the effect, and the CompiledEffect to the appropriate compiled effect. Then just call SetTexture() with the textures I need in the effect.
Except SetTexture() is protected, so I have to derive to XEffectMaterialContent to be able to set the value.
Except when I do that, the automatic serialization of EffectMaterialContent breaks.

So how do I use this class properly to write out a compiled effect with parameters, and read back in an Effect instance with the appropriate textures?

EffectMaterialContent.Textures.Add("yourKey", new ExternalReference<TextureContent>(yourTexturePath));

Maybe? The content pipeline is pretty powerful, I wish I knew more about it other than what I've seen in the samples.

Yes, I actually found this out by reading what the XFileImporter did using the .NET Reflector :-) Curious that the collection is public and can be modified, but the SetTexture() function is not, but there you have it.

Now, if only I could figure out what magic incantations I need to sing to make a usable, configured Effect instance come out the other end, without having to duplicate all the work of the content pipeline myself...