As explained in the SDK: no that is not possible.
Thanks for your answer, Chris. Where can I find it in the documentation? It is a huge package of information and I couldn't extract that piece you've mentioned.
It is very unfortunate that it is not possible. Photoshop is lacking of so much procedurality.
The SDK explains the kinds of things you can do.
Anything it doesn't say you can do: you cannot do.
And creating a plugin that could render a layer without comprimizing performance and stability of the applicaiton is a lot harder to do than it sounds.