Hopefully others will weigh in with their thoughts. I'm new to this leasing stuff.
You could pay out that cash in two phases over time in two ways instead of all at once. Choices:
1. Lease to get $7.5k credit off MSRP. Ask for lease buyout option and pay off lease right away with cash.
@borski isn't this what you did with your Ioniq 5?
2. Lease to get $7.5k credit, pay lease over however many years you decide, look at residual value, and decide to either pay residual with cash or find a used Gravity (if lower priced than residual on your lease) and pay cash. One challenge is finding the exact used Gravity with the features you want and decent mileage. Exploring a lease option can't hurt. Get details and then decide.
Of course paying cash upfront saves you more on interest costs during a lease than the $7.5k credit unless immediate lease payoff.
If you definitely know you want to keep your Gravity, consider a slush fund for future battery replacement. Who knows, by time one is needed the price should be quite a bit lower. By time the warranty expires there should be new battery tech.