I do like the idea of giving a player who is supposed to get caught due to bad information to have a time limit so that if he gets in and out fast enough he'll get away with the operation.
And indeed, that is exactly what I did.
I tried another short test game. Start set-up: nation Britain, character type Sailor, ship Lugger. So no LoM, no Merchant Licence, no particular boost to combat or trade, and a basic little tier 8 ship. After stocking up on food, rum, planks and sailcloth (probably overstocking - usually I start with something larger), I didn't have enough money to buy a cargo, so I took a cargo quest from the storekeeper, to deliver something to Pirate Settlement, Nevis.
Hint: if you're going to Pirate Settlement, fly a British or allied flag. Coastal traffic is based on the "smuggling nation", which is Britain for the whole island of Nevis. Sometimes you'll run into enemy raiders but more often than not, if you meet something near Pirate Settlement, it's British or allied. In my case it was several ships, a couple of them quite big - I don't know exactly what type, they weren't attacking me so I didn't care. After delivering the cargo, I had enough money to buy some cinnamon and sandal, then headed for Guadeloupe. Out in the open sea, well away from any fort, I switched to a false French flag.
At Guadeloupe I did the usual business with the smuggler and a drunk soldier, then went round to the beach and landed at the recommended time. The soldier's info was good; no coastguards appeared, and I made a nice profit. Back in town, I stocked up on silk and headed for Puerto Rico.
Puerto Rico is a particularly risky destination because the smugglers are part way up the path, so you're likely to be attacked by the bandits who live on that path as well as the coastguard if they turn up, which they did. Fortunately the bandits who weren't attacking me slowed the coastguard down, unfortunately not long enough. I had enough time to finish business with the smugglers, killed a couple of bandits, and ran away from the coastguards. Back to town, where I picked up some ebony.
The coastguard also showed up at Jamaica. But the smugglers there are closer to the beach. Knowing that the coastguard can show up if you wait too long, I'm in the habit of getting through the dialog as fast as possible and then running for the boat, so I was already halfway there when the guards appeared. So long, suckers!
So, three smuggling runs, coastguard soldiers appeared in two of them, coastguard ships never showed up at all, and this is my record sheet so far:
How I'd improve smuggling:
1: Get rid of the "Smuggler's Life for Me" sidequest. Or at least, separate it from the opium smuggling and maybe turn it into a tutorial quest similar to the ones for international relations and pirating.
2: A bit more variety in the tavern soldier's dialog. He's got to be wondering if I'm ever going to get lucky with the barmaid, and anyway that line doesn't work too well for a female smuggler.
A random choice of lines could make it a bit more interesting.