Very impressive theory Fairthought. I wonder if the top think tanks in the US/Taiwan/Japan ect. have thought about it...
Anyway, another factor to consider would be what the chinese are drilling through. If it's soft soil, they would have to deal with flooding, structural and various other issues. If it's hard rock, it could take considerably longer than 30 years and the budget will be astronomical.
If china can pull it off, it'll definately go in the books with the great wall and other great Chinese accomplishments.