What I think could be done, however, is that Larian offers the whole game for testing to some dedicated players and fans under the condition that they are not allowed to talk about the final chapters of the game here on public forums.
Closed beta is not a bad idea if done properly, like those betas where devs gather a wide variety of participants with different pc specs. However, I'm not sure it's fair for the rest of the backers who are eligible for beta.