The proposal for building a cable stayed bridge as a replacement has much merit. By placing the support columns way back in shallow water appears a good protection from a repeat incident. But still some protection from runaway barges will be needed. AS well construction will be faster than a standard truss bridge. I do hope that ship owners and operators are held fully liable for all costs but suspect. If so, that will probably mean a bankruptcy will be the result.
Have no idea if any columns of remaining bridge will be useable as each column will need extensive surveys to find any hidden damage. Aswell, the higher clearances proposed for the cable stay may preclude using of the old bridge piers.
This requires a full engineering analysis, not educated (or uneducated) guesses. My uneducated guesses are that a cable-stayed bridge has the road surface much closer to the bottom of the span at the piers (there is lots of truss between the top of the piers and the road surface) but the truss itself in the middle of the span is much thicker than a cable-stayed bridge*. To keep the same clearance height above the water, the piers would have to be significantly taller, but perhaps not as much as it might appear because what matters is the vertical clearance between the piers, not at the piers. The truss is thinner in the middle of the span, but the thicker part at the piers extends out a significant distance on either side of each pier. The bottom side of a cable-stayed bridge is much closer to flat and level (compared to a truss bridge) between the piers, which would make the clear channel between them much wider at a lower height.
The piers need to be much taller to support the cables, but I suspect the pier columns are much lighter, especially as they are thinner at the top. And the bridge itself would be much lighter, I think. So the existing piers (if undamaged) might be strong enough to serve as the foundation of extended piers for a cable-stayed bridge. As I said, this requires an engineering analysis. (Maybe an experience bridge engineer could look at the specs and requirements and say in a very short time, "yes - no problem", "no way", or "maybe". I suspect "maybe" would be the most likely answer.)
Perhaps the answer is yes, but it would still be cheaper to build new piers for a different type of bridge. More analysis.
I think a cable-stayed bridge or a traditional suspension bridge could have much longer span placing the piers in shallow water or even on dry land, where they would be safe from boat collisions. Is this sufficient reason for abandoning the existing piers, even if they could be repaired or don't actually require any repairs?
Maybe the requirements have changed and just rebuilding the bridge as it was wouldn't really be the right thing to do. Does it need to be taller, or is it taller than it needs to be? Is it sufficiently wide (enough traffic lanes), or should it be wider? Or narrower? Are the piers fine, but of limited lifetime, so the whole bridge would still have to be replaced in the not-too-distant future?
Finally of course, the ultimate question: "Does Governor Le Petomane have a cousin in the concrete or steel fabrication business?"
[*] I'm worried that I'm not describing what I am picturing here very clearly. The truss of the center span of the bridge (the part that sits on top of the piers) is much thicker than a cable-stay bridge, but the thick part is at the piers, and the center of the span (which is where the ships need clearance) is a lot higher than the base of the truss at the piers. The unobstructed span of the cable-stayed bridge is almost the entire space between the piers, whereas for a truss bridge, the truss obstructs about 1/3 of the span at each end, so only the middle third is unobstructed.