Yes this would seem fair, maybe have it as a Capitol tech (costing 3000 food, 3000 coin and 3000 wood) which increasing all military units attack and hitpoints by 50% and be used to act as a stalemate breaker at the end of a long treaty game. This would apply to all infantry, cavalry, artillery and ships.
Alternately, this capitol tech could instead decrease the rate of fire for all ranged units to 1.5 (from 3) and also increase their overall range to show technological advancement. For instance, Redcoats could now be armed with Martini Henry Rifles (1871), which increases their range to 16 (from 12) and RoF to 1.5 (from 3). Ships could just fire two canons at a time rather than one to show improved naval gunnery. And maybe Maxim Guns (1884) could become trainable at the Artillery Foundry.
And yes this would seem a fair way to show British naval dominance in this time period.