As has already been said, I see no need nor reason to increase the span width or height opening. Either, particularly vertical clearance would require far more work than simply replacing the existing structure. I also doubt that there is any foundation damage to the pier that was struck. In fact, the easiest and simplest would be to replace the steelwork "in kind". As to the piers, the above water portion of the destroyed pier should be replaced with a much stouter solid structure, and while at it, replace/reinforce the pier under the other end of the main span to be similar. The type framing in the existing main span piers I would regard as having insufficient strength against impact compared to any bridge over the Lower Mississippi built from the first one that opened in 1892. The major need is a much larger solid surround of these main piers plus two or three very stout dolphins both upstream and downstream of this main span. While at it, place dolphins upstream and downstream of several of the approach span piers. The larger surround (there is probably a proper name for this, but I don't know it) of the main piers should be designed to take a strike of a ship some 50% larger than the current ships at 8 to 10 knots. A ship speed limit should be imposed.
