First, unlike most lock systems, they will have to operate against the natural influx of the sea, not with it, which will demand pumps instead of gravity flow to drive them. So in addition to building the locks, we'll have to start engineering the Farallones Offshore Windmill Farm to supply an inexhaustible, nonpolluting source of power.
Second, the Golden Gate Locks will not just allow ships to pass into the bay but will also artificially maintain the bay's tides to preserve the wetlands and to prevent the demarcation between saltwater and freshwater from shifting too far up into the delta and wrecking all the great bass fishing. The entire output of the Sacramento and San Joaquin rivers will have to be pumped into the sea, as not a drop of it will be able to defy gravity to flow into it. This will require larger pumps than we could buy off the shelf at Home Depot. Again, more reason to start thinking about all this now, not later.
Finally, there will be the matter of what color to paint the Golden Gate Locks. The history of contention over the color of the Golden Gate Bridge reminds us that settling this important detail could tie up the entire project for years. That the Golden Gate Locks invariably will wind up being called the Goldi-Locks could shortcut that decision.