Great! As I said, the rest of the government structure is outside my understanding, so I can't offer suggestions (in fact, the "swapped Connecticut" came to me only because I read Wikipedia for inspiration and explained it for dummies).
Also, not to dismish Bennett's work, but I have made rough proposals for the River Plate Colony (
name pending consensus) on the early 19th century:
1) Minimalist: the UK takes Buenos Aires and its immediate hinterland and nothing else; Brazil doesn't invade Banda Oriental or is repulsed/forced to withdrew.
2) Minimalist+Cisplatina: else as above but Brazil invades/manages to hold Banda Oriental as Cisplatine province.
3) Medium: apart Buenos Aires and surroundings, lower Mesopotamia is also captured by the British.
4) Medium+Cisplatina.
5) Extensive: both sides of the River Plate and their hinterlands, and lower Mesopotamia to conect them, are secured.
6) Expansive: the above plus some northern Banda Oriental del Uruguay.
I tend to favor 2), 4) or 5), but OTL Uruguay-Brazil border bothers me, I haven't been able to come with a better alternate. Also, ignore the rest of the borders of the would-be Gaucho republics, are just placeholders, previously present on the map and not modified.