Hi Stefan!
First, while your idea is noble, I hate to say it is very far fetched. The hundreds of square yards of finished oak for the paneling alone would cost a small fortune and that is without the expense of having it carved and installed. The wrought iron dome would be another huge expense, not including the marble tiling. It is just not financially feasible for anyone other than Bill Gates to attempt to recreate something as grandiose as the Titanic's Grand Staircase.
Second, I am not certain that the blueprints and carving guides for the Titanic's interior are available to the general public, so many of these documents were lost or stolen during the Loss Inquiries and are probably either locked away in Harland & Wolff's vaults or in private hands. The best you could do is to find the source Cameron used for his movie.
Brian