Hi
I'd say Caterham, Caterham, or maybe a Caterham (having had 3 in increasing outputs

)
You can of course only go as fast as the car in front if you can't overtake. But,
The huge difference with this car over pretty much any other is removing the windscreen. Then you get to experience so much of what is around you that putting a lid on and getting on a bike is a step backwards. Like going from a 12" portable TV to a 70" whoppa with surround, maybe flames too depending on the injection system

Decent sunnies required though.
I had two normal sized ones, and did many 2 up camping trips mainly to France. Some compromise required. The last one was a wider body which is I think only 3" longer and wider but frees up much more space for stuff. Luxury!
A friend had an Elise and I would agree its hard to get out of with the fat sills, but thats not the case on a 7. Roof on it does need a twist to get in or out, but if you take a lid and waterproofs for when it rains no worries.
The screen is held on with 4 bolts, an aeroscreen bolts on instead, so if SWMBO insists swapping is easy.
I'm sure most here will say it would be daft without a lid anyway, or its too small/cramped/dangerous etc etc, but I would encourage anyone to go to one of the few dealers and get a demo, or find someone with one and go for a ride, even just the once. Mucho fun
Cheap running costs too for most models