I've noticed something. The shop's openings and closings are entirely dependent on threat level, and don't give a fig about walls. You could have an Outpost with 86,528,703 Defense Hitpoints, and if it gets to Interesting Times, things shut down and plunge into chaos. From a Story standpoint, this makes no sense. You can have all the monsters outside you want, but if you're in no danger of breach, why bother not selling things? Selling things makes you money!
From a gameplay standpoint, it also makes walls mostly irrelevant, or, dare I say it, counter-productive.
Walls, at the moment, only affect anything at the highest threat level, and then only serve to delay the Outpost's breach. I assume it is quicker to reduce the monster levels in a breached Outpost than a non-breached one, so an Outpost with no walls would dip into breach a lot, but it'd be a very shallow breach, and easily beaten down to Critical Situation. Meanwhile, the Outpost with walls would stay at Interesting Times (meaning less shops are open) which would build and build as the walls decay until, like a simile you examine too much, they finally break and unleash a gigantic insurmountable pile of monsters on the Outpost, leading to those feelings of hopelessness.
Now, I'm not entirely sure what I've said is true or valuable, because I'm a bit sleep-deprived at the moment, but I have a solution to the above problem of walls being counter-productive. Make shops only close down if the threat level says they should and the walls are below some given amount. 5,000, maybe?
One thing that a wall at the highest threat does give us is access to the pubs, so they're not entirely useless. But - that's it really. I don't generally work on walls, and I've been happy to see a lot of them zeroed (sadly, they'll just get built back up again into the hundreds of millions...) The only place where I think it's worth building up walls and defending the place from titans is Cyber City, because of the Scrapyard. Everywhere else: yes, I agree, almost completely counterproductive.
Keep in mind the fact that a breached Outpost is a deathtrap for low-level or poorly equipped characters. There's no display, really, that warns folks away, so having the walls there keeps people alive.
In addition, Joe's Dojo for the respective race, the Common Ground, the Pubs (as mentioned before by Ada) and various other city-specific resources are available to a city with walls... they're hardly useless. Walls allow lower-level characters to stay and fight for their homes, folks who can survive Jungling and can use the extra Req payouts but wouldn't last long in a Breach... and that is by no means a bad thing.
After all, we're all periodically in that low-level, ill-equipped group, as long as we're hunting the Drive.
Don't forget Dan's Quest.
You can Danquest in a breached outpost - just enter the jungle directly, instead of going to the outpost first.
Nekops: Joe's Dojo closes at level 8, before the walls are breached. The CG is accessible from everywhere, so it's not a huge loss if it can't be reached from one outpost. City-specific things usually close at threat 7, so they're down before walls are, too. I believe the only exceptions are the ones in Cyb and IC.
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