Idea for allowing non-permitted items in carry-on; service from airlines or TSA
I had this idea and I wondered whether it would be feasible, or desired by enough travelers to make it worthwhile to airlines or the TSA. It's for them to provide a lock-box that can be put in your carry-on at your origin airport and removed at the destination, for a fee, to allow you to take items on-board like blades or pointed items (thinking toolkits to technicians) or even guns. Many people travel light and aren't checking a bag and doing so just for such an item that they need at the destination is silly, especially if there's a checked-bag fee, or they don't want to risk a checked bag being lost on the way, and if you're just on an overnight or short trip you don't have a lot of luggage. (Of course they're heading towards fees for even a carry-on bag or just allowing anything at all aside from a personal item for some fares, but this service could be permitted as a separate item. The fee would have to be less than just checking a bag, though.)
I was thinking when you book your ticket, you add the option to get a lock-box. You check in at the security office or airline desk when you get there. They open a box, you put your stuff in, they lock it and it goes in your carry-on. This would require the agent to verify the contents aren't something that would be dangerous even in the box, like flammable/explosive or a loose battery. You have no access to the contents, and it's a reasonably strong container so you couldn't just break it open during the flight. There'd be a size limit of course so it wouldn't work for everything. At your destination you go back to the desk and they unlock the box. It's done with electronic locks of course, controlled with a computer connection assuming they can make it super-secure so people couldn't hack it, or a really secure physical lock and key that can't be picked, or combination, or an electronic number pad. (16-digit combination? 24? So they can't try every combination during the flight. Electronic pad could prevent trying many in a short time. Changed with every use.)
Potentially they could be sold at retail, certified with a way for the security/airline desk to verify it and then set the security, like TSA-approved padlocks that they can unlock. Again would need to be done so that nobody could fake the certification, and adds work for the agent and TSA and airlines certainly don't want to have to have more people working.
I don't know if it would be really popular, but for some people it would be very useful. I worked as an IT tech and sometimes had to make trips on short notice where I would need tools. A cheap screwdriver can be picked up on the way to the site after landing, or already be available on-site, but many of the tools I might need would be unlikely for a site to have and cost hundreds of dollars (with no way of knowing if I'd need them), and overnighting the kit would be just as expensive and might be unnecessary if I didn't need those tools. I didn't end up ever having a problem, being allowed to carry some small items in my bag and then the sites having others, but that was due to the type of sites in those cases and wouldn't always be true. Other people might be the type that likes to have their gun with them and be traveling to a place where they'd be permitted to carry it (and that type would be very likely to be willing to pay for this service).
Given the extra work for the TSA or the airline, I'm not sure if the volume of customers would actually make this able to break even financially, let alone be profitable, without making it stupidly expensive to the customer and reducing the number of people who'd use it.