Lift it and put some PSC Brawler Rockers on it! (kinda joking but, seriously, a rocker product such as those adds some serious beef to the sides (though legally no manufacturers will make any claims along those lines)) The lift will keep the average car from encroaching into the passenger area though, a beefy cage will be in order since the Jeep will likely end up on its side (since it will no longer absorb the impact, the inertia needs to translate into movement). On the plus side, a beefy cage will also add strength since the pillars will be stronger and further help prevent the other vehicle from entering the passenger area!
In all seriousness though, if you want side impact strength, look elsewhere than a Wrangler. By design a Wrangler has a narrow tub for trail clearance and since it still needs to have room inside for people, the side body panels must be slim. Not saying it's a horribly unsafe vehicle (there's definitely worse out there) BUT, there are definitely safer vehicles to be had!!!