I would like to remind you folks that this is not our world. This is a world where massive armored, heavily-armed airships are functional. Where there are materials that literally defy the laws of gravity (ie. Floatstone). I would further point out the terrain of where it's intended. The land contains three major bodies of water in a relative line and no doubt can be inferred to consist of numerous rivers connecting them. Such a design is similar to the canals built in Scotland connecting previously extant Lochs and river systems to produce functional travel from Northern Scotland into the waterways around Glasgow. Furthermore, I would point out the technology level. The ability to produce titanic industrial excavators beyond the scope and comprehension of even modern technology mankind is there, as we've proven with the truly immense weapons of war. As stated by Skepic in the OP,

"The Great War Machines! Now war is always fun to have in NRPs, and I am going to be very liberal on big nations possessing some massive war machine. However, the few restrictions I will apply is that you can't just whip it out on every battle and they will be generally be slow moving. Other than that, go nuts! Just understand they are not really there to win your nation a war, but to add to the world and have a Goliath for David to face."

If this still stands, which I have no doubt it does as is shown by the acceptance of the massive tower made in Esperi that houses millions, then I have no doubt that the ability to make a canal using the economy of two countries, an immense international organization, and all their shared industry with already existing waterways is more than feasible.