the safety between my ears tells me that the safety between my ears isn't perfect.
Yet your belief in the superiority of having a manual safety is "firm and unshakable" even though the device is there to merely ameliorate the risk (and only part of the time, at that) of the hair trigger that many, albeit not all, such handguns have.
The bottom line is that ultimately you cannot
rely on mechanical safety features, which are only there to supplement the so-called safety between your ears, or rather your discipline in handling firearms. There are tradeoffs involved with virtually everything you do. For instance, I would submit that for some people making the operation of a handgun simpler would help improve the consistency of their firearms discipline and reduce the number of mistakes they'd make. The main reason that people sometimes forget to take a gun off the manual safety when ready to fire is that they're so intensely focused, and rightfully so, on following the safety rules rather than operating a mechanical device. Of course, such a mistake can be made exceedingly rare through training, but it is still merely an aspect of operating a specific machine, over which the fundamental safety rules always take precedence.
I realize that your intention is to layer different types of safety measures on top of one another as reinforcement, but in your original post, you implied that you'd be fine with the very light, short trigger pulls that many handguns equipped with manual safeties have. This is not unusual or wrong in any way, but I'd like to note for the sake of perspective that it marks a specific level of risk that you are willing to accept, and that there are other people who take even more precautions than you're envisioning, such as combining a manual safety with a "safe-action" (trigger safeties) pistol, which is probably the most popular configuration of the Smith & Wesson M&P in law enforcement currently, to take one example. There is no absolute way to prove that a gun that has a single-action hair trigger and a manual safety is safer overall than a gun that has trigger safeties. For one thing, you can't know for certain at any given moment whether the manual safety is still on--that you remembered to activate it and that nothing has accidentally deactivated it since then--so you still have to keep your finger and other objects away from the trigger. Having a longer, heavier trigger pull is arguably just as safe overall, provided that you follow the same fundamental rules. And once you deactivate the manual safety, then all of a sudden you have to rely more than ever on that fallible safety between your ears that seems to make you so nervous. That's what I find somewhat disturbing about your faith in the superiority of manual safeties and possible lack of faith in your own firearms handling discipline. Under the tremendous stress and adrenaline rush of a gunfight, would you really be safer with that hair trigger or a gun that has some safety built into the trigger at all times until you deliberately squeeze it with some force over some distance? I'm not just talking about your own safety here, but also the safety of those who may be present but should not be shot. I'm not trying to tell you what's right for you or even what's really better--I'm just putting things into perspective.
Now let me give you my personal perspective. When I started the process of buying my first handgun, I had pretty much decided ahead of time that I wanted a single-action-only or double-action/single-action semiautomatic pistol with a manual safety so that it could be kept in Condition 1 (i.e. cocked & locked). After trying a bunch of different pistols, including revolvers, while keeping as open a mind as I could, I ended up with a safe-action polymer pistol with no manual safety, and I consider myself a very conservative type of person when it comes to safety. I found that the trigger pull has no affect on combat shooting except to make things just a little safer and more deliberate on my part, I liked the fact that the safeties are always on except when I deliberately pull the trigger (and trigger discipline is one of the fundamental rules), and the simplicity of operation gives me one less thing to worry about, making that fallible safety between my ears a little bit more reliable. This sort of system has worked fine for double-action revolvers for many decades, and it works fine for semiautomatics and me, too. I'm not saying that you have to agree and change your mind, but do learn to rely on yourself before relying on a manual safety--it's only there because some triggers are unforgiving of even the most minor of accidents, not because it's inherently necessary for the safe handling of all firearms, or superior to all manuals of arms in general.