Of course, i agree! You can help me for the changelog and for the translation mistakes in the game too.I could provide a proper English translation of the change-log if you wanna.
First, thank you for your message, I am always happy to see somebody is interested in the developpement of this mod.
-Difficulty levels: Indeed, there are many problems in this mod, whose some of them come of the original game. So there are work to improve this game part.
-Forts: I didn't test this mod, so I can't really answer you now.
-Colonization: The following version will arrange all problems you said me.
-Naval stock: In the new europe screens, we can only have directly a ship that if we buy an used ship, otherwise we must wait some turns to get our ships.
Why not!*Carracks: increased tool costs to 40 or 45. Increased production points to 150. Increased cost in Europe

I agree but this is not in the following version that i will do it, but i already thought to this idea.*All merchant ships should be able to attack, with 3/4 strength modifier, at some point when the king gives you "ammunition and cannons for your fleet". Disadvantage can be added to the defender if the unit have not this ability.
If you find the art files of this units, I will add it in the game*Parallel to the construction of galleons 3 new generic military or trade ships should be added to the 2nd period.
-Sloops: 40% against galleons. 7 strength. 5 movement. Military unit.
-Brigantines: 20% against merchantman & sloops. 6 strength. 7 movement. 1 cargo space. Trade/military unit.
-Hookers: 30% against brigantines & sloops. 10% against merchantman . 5 strength. 6 movement. 2 cargo space. Trade/military unit.

Of course, there are many work and I don't have many of time to work on this mod. So we must be patient. Your ideas are obviously welcome!if you want a complete revamp of Col 4 in all the aspects following your project.