Not gonna comment on getting a IS vs ES (two different cars, but the new ES is a LOT better than the 2013-2018 version… But nowhere as sporty as the IS/GS line), but you can roll in negative equity into a BMW lease or any other lease. The Lexus dealer (not Lexus financial/corporate) is buying the car at $28500. They tack on the negative equity ($2700) on the new car. If the RC is worth $28,500, then you should have no problem having a BMW dealership buy the RC for $28,500 and roll the $2700 negative equity into a new BMW or any other manufacturer of your choosing.
FWIW, the IS isn’t available with Apple CarPlay… Something to think about since most other competing cars have it available… Why I personally went the Volvo route over the Lexus route (some newer Lexus lines have CarPlay… the 2019 RX didn’t have it available)