SOLVED: I found the missing ship blueprints in Einar's shop on my own ship. It's the guy that sells stuff for the weird special coins.

I am wrapping everything up before the final boss fight of the game.

To my surprise I realized it doesn't allow me to finish upgrading my ship. It says that there are no new proposals or something like that.

In the stats of the ship, I'm missing 1 bar in each:
Ex-Arm Power
M Barier Potency
M. Sail Acceleration

I have the Carnac achievement, so it seems I have all the Carnac citizens rescued.

Edit: I found 2 missing proposals on merchant ships, but still missing something that I have no idea where to get...

Edit 2: I am done with 100% world discovery, so it's nothing in a chest or anything like that.

Here's a screenshot of the stat page. Any idea where I can get the missing proposals?
https://imgur.com/Jw3T8e6