City Port (Name in progress)

I a sure i wouldn't be the first to say that there are tons of shipping games available,I hope your unique twists will set it apart. Any game will be a good practice in game design i would guess, i am new to seeking publication as well.
Many of these types of games in my experience can be fiddley or complicated to some so the audience may be smaller as well. Always remember you can have the same game you created but change the theme to something less
saturated.
Keep going and hope you end up with a streamlined, unique product players will want in their collection.
Good luck and hope you receive useful and inspiring feedback.

I would stick AWAY from "Medieval Merchants" style of game. This is an over-populated theme and it would be better if you went with something like a more "current" feel...

One thing if it is more current, you could have cruise ships and instead of delivering goods, you could earn income based on the number of passengers that take the cruise.

Perhaps a "cruise" concept could be something worthwhile exploring. Again just some ideas - because the other theme has been overly-done.

Not 100% certain HOW you would design a "cruise" themed game - but it may be something you might want to explore! :)

Note: Passengers could take optional tours at each port, helping you earn more money - because the tours would be hosted by the cruise line. Or something like that... Personally I like the idea of a "cruise" board game... I think it's different. I searched BGG and found a few games that are "cruise" related like "The Love Boat" or "Mediterranean Cruise", but there isn't a HUGE amount of "Cruise" games out there already...