Any of you full-timers also bring a separate car along?

Rules vary by state but you can double tow with a 5th wheel.

Of course, the Nissan is marginal for most 5th wheels. (pin wieght typicaly controls not tow rating). Full time, you will likely have a lot of stuff, so you realy have to watch the weight.

I would lean toward a toy hauler for simplicity.

Another option is a travel trailer and jet ski in the pickup bed (they make ramps). This assumes it's not a giant jet ski that sticks 4' out the tailgate.