If we ditch the big-city format, we can be safe from WMD's. A small-town format would work fine. There are not enough people in small-towns to warrant the use of a WMD. The small-town format is already a working, economical structure. Although, in the small-town format, there could be targets for smaller munitions.

Target 1, Schools: By using the internet, the school-system could be modified so students no longer congregate. Through the use of webcams, a student could easily and interactively participate in almost every normal class function, without leaving their home.

Target 2, Movie Theaters: I doubt people care much anymore about theaters. If you did an experiment, where you released new movies to both theaters and homes, theater sales would likely 'plummet'. With all the big-screen tv's, and the comfort of your own home, it's tough for dirty, crowded theaters to compete. The whole theater system could be scrapped.

Target 3, Sporting Events: Yes, for most sports, it would be odd if there were no crowds. It could still function though. Most people watch sports through their home televisions anyway. Non-professional sporting events do not usually generate the kind of crowd worth bombing. Another solution is for everyone to quit physical sports and only play online esports (this would obviously be the most preferable solution for everyone).

Target 4, Markets: In small-towns where i've lived, markets are never crowded. They could easily be organized so they are less crowded. In today's world of computers, the internet, and home delivery, most or all things can be acquired online anyway, where there is no risk of bombing.

Target 5, Hospitals: Small-town hospitals are small. They're usually one-story, and there are never many people there. Not much of a target to begin with, and could be less of a target if desired.

Target 6, Bars/Clubs: These could be minor targets. Neither are necessary, both could be scrapped without too many people caring. You can get drunk at home. You can dance at home. You can listen to music at home. You can have friends over to do all of those things with you. I don't know that you could secure these types of things, considering the main point is to congregate. Even if you check people at the door, they can just shoot the security people, run-in and suicide-bomb everyone. Or, they could break-in when things are closed, plant the bomb, then detonate when the place is packed. And those are only two methods of bypassing security. Furthermore, a military-grade missile or bombing attack would render all typical security worthless.

Target 7, Restaurants: These things are not needed. You should not trade freedom for security, but it's possible you should trade luxury for security. A delivery restaurant would still work fine. Catering would also be safe. Because your car functions as armor, drive-thru would work.

Target 8, Work-Environments: With the addition of computers and the internet, most work can be done at home, remotely or otherwise. Most other work does not require congregation. If people made an effort, i'm sure working conditions could be secured fairly easily.

Target 9, Apartment Buildings/Hotels: In small-towns, these things are always too small to be worth bombing. Like the hospitals, they are usually around one-story.

Target 10, Churches: In this one case, more congregation = safer... really. Trust me, church-people, especially Christians, you should gather together. The more people per square-inch, the better.

I can't think of any other targets. These should be enough to go on. As you can plainly see, we do not need to put our selves at risk. Nuclear weapons, other WMD's, and bombing in general, do not need to threaten. Most of the reason these things are a threat, is because people value luxury over safety. The rest of the reason comes from simple economics. With modern technology, old economics no longer apply. Utilizing new technologies, safer systems could also be more economical systems.