Set renderable objects on camera without Layers

So, what's wrong with using render layers? It's like asking "I want to nail together this box, but I don't want to use a hammer"

Because sometimes you need a screw ;)

If I use render layers I will either have to have a layer that's always reserved for an action that will not run that frequently or assign a layer to each object and camera pair, which is more than a little silly.

I will mostly render a single object to a camera and reserving a render layer for that seems a bit excessive.

I can work with the reserved layer thing, however, ideally I'd like to say something like: Camera.Render(Renderer[]); which doesn't exist obviously but it would be nice.

Why, exactly, are you doing this? What's the desired outcome?

I'm writing a system that will automatically convert any renderer into impostors. So I need to be able to render an object on it's own without outside interference. I've got most of it working, right now the biggest headache is the fact that multiple objects can be rendered when I just need to the one.

I have a similar problem with multiple objects needing to be rendered on regular intervals on their own for later use. With OpenGL I put together a little routine I would attach to all the object that needed that, with Unity it seems impossible.