I would take a different approach...

Of course, the ship classes are very close. Still, I really want to make a distinction between the older 90 and 98 gun ships and the Dreadnought class and the Boyne class of 1810 and of course the 1st Rates.
For me, technically speaking, the strength of the hull is the first distinguishing feature. And while it may sound weird at first, I think the older 90/98 gunships should be referred to as hull 5 ships rather than hull 6 ships.
I have the tonnage (bm) in mind. At about 2100 bm the limit is reached for me. See the heavy 2-deckers (84 guns or similar), super-heavy US battleships Independence, etc., and all 1st rates. All these classes/ships have hull 6 and 10 or 11 boxes with 60 or 66 points respectively.
This is also supported by the armament of these ships. The later models and 2-decker had significantly heavier guns on board with higher damage output.

Also, it bothers me that beyond the hull 6 with 11 hull boxes there is no option for an increase. I would put the big 112/130 Spaniards or 120 French on the same level as the old 90/98 British.
Of course, combat power can be adjusted - but I tend to make a difference in hull strength as well.

I would give those 90/98 gun ships more hull squares for that. Since the normal 74s with hull 5 "only" have 9 boxes with 45 points, there is still the possibility of increasing the fields. This in turn reflects the bigger teams!
For the sake of order, mention those old ships as well. Although they don't play a significant role for me because the Union + Neptune were demoted to port service and the Namur was later converted to the 74:

HMS Namur (1755), HMS Union (1756) and HMS Neptune (1757) are the oldest, which were no longer upgraded to 98s = hull 5 with 10 boxes = 50 points

All ships of the Sandwich, London, Barfleur, Queen, Duke, Londen (revised) and Boyne (1790) classes are all below 2100 bm in design and tonnage (bm). Therefore I would give these ships 5 but 11 boxes = 55 points as a hull.
Of course, there are other distinguishing features in combat power, etc.

The dreadnoughts (Dreadnought + Neptune + Temeraire) are just reaching the limit. However, I would like to have some distance between the 1st rate ships.
Therefore these hulls would have 6 - but only 10 boxes = 60 points!
The Boyne class (Boyne 1810 + Union 1811) with the Victory based hulls are above the 2100+ and would therefore also have hulls 6 and 11 boxes = 66 points! They are ships that would qualify as really 1st installment.

That is an option. I'm just trying to create technical differences.
Do you think that's total nonsense or are we going to get any further.