It should work Mr Musk, if the welding machine can be designed
to withstand the pressure of the water.
Then you've got the sides that are welded,
and front and back that will be welded as well,
creating a type of 'container' that will bring up the ship.
I hope this works Mr. Cameron.
I think, overall, it wouldn't cost that much.
If my interlocked wooden ships, (plated with very thin alumium sheets, in order
to keep the glue from being in contact with the water)
they are most likely very cheap to build as well.
So this would be the most cost-effective and efficient way to retrieve the Titanic.
Another factor would be electricity running through the wire that descends,
but I don't think pressure of the water will affect the electricity/wires.
If the drill and the welding machine can handle the pressure, it should work...