I think that Musketmen are completely useless in the game, as Grenadiers are a lot stronger (12 instead of 9 HP) with an inherent +50% attack bonus vs. Riflemen, and Musketmen are immediately succeeded by Grenadiers in the tech tree.
I think that Musketmen should be improved by adding them some inherent bonus such as +50% vs. Archery and Melee units, then they would be better against these units (9x1.5=13.5 HP) than Grenadiers with 12 HP. Another way to improve them would be to give them +1 HP and, say, +25% vs. Archery, Melee and Mounted units. This would pretty much resemble the 'stone-paper-scissors' system implemented to the units in the Ancient Era.
The same could be applied to the French Musketeers with 2 MP, then perhaps they would compare to the English Redcoats or the Russian Cossacks in usefulness. Ottoman Janissaries could also come with e.g. +1 more HP compared to the improved Musketmen. This way, the French and the Ottomans could have decent unique units in the game.
I think that Musketmen should be improved by adding them some inherent bonus such as +50% vs. Archery and Melee units, then they would be better against these units (9x1.5=13.5 HP) than Grenadiers with 12 HP. Another way to improve them would be to give them +1 HP and, say, +25% vs. Archery, Melee and Mounted units. This would pretty much resemble the 'stone-paper-scissors' system implemented to the units in the Ancient Era.
The same could be applied to the French Musketeers with 2 MP, then perhaps they would compare to the English Redcoats or the Russian Cossacks in usefulness. Ottoman Janissaries could also come with e.g. +1 more HP compared to the improved Musketmen. This way, the French and the Ottomans could have decent unique units in the game.