During the war of 1812, some of the most vicious naval battles were fought on the Great Lakes, including the famous climax of the battle of Lake Erie, where Oliver Hazard Perry lead an American flotilla to victory over an similar assortment of British ships ("We have met the enemy and they are ours"). However, even in that penultimate battle on the Lakes the largest combatants in both "fleets" were brigs and schooners, because due to the Niagara falls and (for any ships on lake Ontario) the impassible Montreal rapids all major fighting ships on the Great Lakes had to be either converted from merchant ships or built from scratch on the shores of the lakes. However, during the war massive ship building programs were commissioned by both sides for building not just brigs or even frigates (like USS Constitution) but fully fledged Ships of the Line, the prime example of which was the HMS St. Lawrence, a First Rate with a whopping 112 guns (more than Nelson's HMS Victory and more than all other British ships at that time commissioned on Lake Ontario COMBINED) which was launched in 1814 from the Kingston dockyard on Lake Ontario. The Americans for their part were building their own major fleet on the lake and had laid down an 84 gun warship, the USS New Orleans at Sackets Harbor, New York, which was laid up when peace was declared.
It seems like with a few tweaks of history in the War of 1812 (maybe either through extending the war or intensifying the laying down of major warships early in the war?), it would have been possible to get a situation involving a major fleet engagement on Lake Ontario, between the USN and the RN and have created the unique situation of having massive wooden battleships fight fleet engagements over the lake rather then the small schooner and brig engagements of real life. How do you think it would be possible to engineer this "storm in a teacup" scenario? And how would the unique circumstances surrounding this scenario (ie. ships limited to a fresh water lake with very limited room to maneuver n a strategic scene) have shaped the potential conflict (would it have devolved into a melee rather than a European line of battle)? Also how would the RN and USN have managed crew these ships? Would they have been able to divert and transport enough sailors from their fleets in the Atlantic to have an experienced crew aboard the "lake warships" or would they have had to heavily rely on drawing from the local merchant sailor populations on the Lakes to crew these ships? Also, which navy do you think would ultimately have the advantage in this unique battle?
Overall this scenario on Lake Ontario feels like it had the potential to be one of the most unique (and frankly weird) naval battles that could have occurred in the last 200 years and really has no similar scenario anywhere in modern Western naval history to draw examples from so it would be fascinating to see how it would unfold.
NOTE: The HMS St. Lawrence was decommissioned in 1815, sold in 1832 and sunk and is now a popular diving attraction. USS New Orleans was laid up for nearly 70 years until it was sold in 1883 (the USN really doesn't seem to like throwing away warships). The Rush Bagot treaty of 1818 demilitarized the Great Lakes limiting the US and Great Britain to one warship (max 100 tons) and one cannon. Later developments such as the Rideau canal made the great lakes accessible to sea going vessels. The Great Lakes remain demilitarized to this day.