I love this ending, it's a nice way to connect this story to both the main series and the real shogunate, and more importantly show them how they adapt from harsh circumstances and grow as people that doesn't depend on the royal family anymore.
It's also interesting to see how guns, that are portrayed only as destructive in the main series, is portrayed in a more positive light. I won't say I agree with it, but I kinda get it.
Though, aside from trading guns and his new-ish ambition, the merchant's ending feels too weak to my liking.
One who cannot see the heart is not fit to be a ruler...
I wonder if that's a jab to Zaganos Pasha, even if not wholly.