WOW! What a great quilt! I am anxious to see it, and would love to see updates as you go if you are up to that. Here are my thoughts, for what it is worth.
I like Calla's idea of the bow heads and immediately thought of going to Google images to see if you can find something there you could trace.
I also like your idea of sampler blocks and would include all kinds of blocks that would 'tell the story'. If you are telling a story with this quilt, such as a sailor leaving home, sailing away to other lands, etc. I would include a log cabin block and find what I could to interpret the story. You could do repeats of the blocks if you wanted to. I also would keep all the sampler blocks in the same colors as the compass. On the back of the quilt, you can write out the story.
Can you tell I am a quilting librarian!? Just an idea. I'm sure you will come up with exactly what you want.