Mexican Empire With A Trans-Continental Canal

Since the days of Hernan Cortes, there has been a dream of a waterway to connect the North (Atlantic) and South (Pacific) Seas. Three options have been considered since von Humboldt revived the idea in the 19th century:

1) Tehuantepec Isthmus (considered first for an interoceanic canal, then for an interoceanic railway)

2) Up the San Juan River to Lake Nicaragua, and then down to the Pacific through locks and tunnels

3) The current Panama canal

There were numerous treaties and purchases made by various imperial powers (France, the United States etc) for the rights to said territory in order to construct a canal. For instance, 1) was included in the McLane-Ocampo Treaty 1859 in which Juarez agreed to let the USA have perpetual right of transit across the Isthmus.

What effects would an interoceanic canal (such as those mentioned (adding that I am aware that the current Panama canal fell within Colombia's borders)) have on the possible economy of a surviving Mexican empire?
 
It would be great for Mexico since they'll be a two ocean empire and face the same logistic and military challenges that lead the US to build the Panama canal in OTL. It's hard to say though what real effect it would have since your POD, presumably in the 1820s, is decades before the technology to build the canal would exist.

I do think that routes 2 and 3 are still the most likely options since the Tehuantepec canal would be so long that construction costs would be enormous even though the route itself might be easier. I think Tehuantepec is likely to see something like what we have now, port facilities at either end connected by a railroad.
 
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