In addition, a quick look at a topographic map suggests that it would have to cut through terrain with an elevation of at least 500m, and that would be far from the shortest route. My guess is that only a sea-level route would be competitive, and a canal using locks would require pumped sea-water to operate them anyway.

Not to mention that a canal would threaten all the aquifers in the region, which already has a major fresh-water shortage.