From what I've read it would have been extremely difficult technically and probably prohibitively expensive to build in 1908.
One of the hardest things is that only a few sketches were ever done and little planning was made on actual structure. I doubt any financier would agree to build something of that size without fairly detailed structural plans. Considering the speed Gaudi worked at I don't think construction would begin for another decade unless he was removed as head of the project.