Oh yeah <evil grin>... just the thing to put the pressure on the PCs, "Get to that ship before the enemy does or else somebody will sink the damned thing - us, them, the locals, who knows but if you don't get there in time it WILL be sunk!"

You could make it even more of a challenge by having the French locate the vessel and put a small group of French Marines on board to secure it. They can secure it but they can't operate it and they really don't have the forces/equipment/intell to stop someone from trying to sink it.

The PCs show up and perhaps someone on the 'shady' side asks them to secure the vessel for a significant reward - do they help the French government/military, do they try to take over the ship for their own profit, if the PCs aren't French do they try to take the ship for their own military?
Some fun to be had with that scenario!

"Thanks
I totally forgot about those Somali pirates hijacking that cargo ship loaded with Russian tanks but yeah, that's another aspect of what I was thinking of - some way to have the vehicles delivered without them actually reaching their intended operator. "

Makes a great way to shake things up in other ways too. As in "where the heck did the (fill in the blank) suddenly get those tanks from?" and then the captured prisoner tells you about a ship full of French tanks and armored vehicles that (fill in the blank) is selling to anyone who has trade goods or gold enough to pay.