So, a good enough dirtpile over the roots should save it? I mean a REALLY good dirtpile, with lots of stone and humus practically building a cairn over the rootball?
There are shops along Hwy 101 in humbolt county where you can buy burls that have been cut off of redwood trees. If you place one in a bowl or bucket of water they will shoot off new sprouts in a short time, and then roots.
Sequoias are hearty trees.