Good point, I was reflecting too much on my own limited experience. And I often play low con/will + high int characters, which makes psibugs' neural overload really scary... it's almost mandatory to keep them from using it.
Indeed, their mechanical threshold will definitely be a problem for melee characters who don't have the str to use off-build sledgehammers, but I find str useful for melee dexxers, or maybe I'm just used to str being a necessity for them. 
But is it really that bad with (metal) gloves and heavy punches?
The mushroom cove base also has some nice spots where you can lure them to a corner or abuse doors, sometimes getting them to reveal their brain almost right next to you before realizing they don't have enough AP left to attack. You'll never have to fight more than one at a time unless you chase them across the base. Instead, let them come to you whenever possible.
On stealth:
The only situation where instant detection applies is when you're trying to cheese your way past too high level mobs, and I bet that's intended. I did manage to trigger instant detection against the lvl10 lunatics with a freshly-created lvl1 character with only 37 stealth, no big surprise there. But I can't think of any other way to trigger it. The stealth requirements don't seem to be high, but I can't test it on very low (<5) level characters without taking the effort to edit some characters.
Here's a random lowbie wearing metal armor, standing almost at their faces, in a brightly lit spot, and still not detected. Not even at orange. lololol.
It is a case of rendering the one and only form of defense of some characters completly useless
Now THAT is absolute fucking bullshit. 
First, stealth works brilliantly if you specialize in it (ie. try to have it as your "only defense"), which you adamantly have refused to do so far. Whatever you say has no relevance until you actually try it.
Second, it will never be anyone's only defense. Speccing into stealth means you have powerful synergies for dodge/evasion and high MPs. Not to mention even leather armors have resistances, even if they are the lowest. In all honesty, CC is the main defense (defense being any method to reduce incoming damage) for all builds.
Well my strenght was 3 because I wanted a quick punching, very high agility and dexterity and depend on dodging + stealth. I know that higher strenght gives me more damage but really, if I want to benefict from strenght then I'd go for sledgehammers. As for the metal gloves, haven't tried them but I don't want them as they have a much higher AP cost, the only reason I want leather gloves is only because I know you always need gloves, pure unarmed doesn't works, especially when you meet robots. Heavy punch, I don't remember if it has a strenght requirement or not but 180% damage for 200% PA cost... Highly innefficient use of AP in my opinion, 2 punches will deal more damage for the same amount of AP (ok maybe not with damage reductions but more punch more crit possibillities anyway).
Yes you never have to fight more than one if you fight them smartly but the point still remains that for unarmed characters they ar much of a challenge alone and if they are not alone you can't even engage.
I tried to reproduce the stealth thing. I was actually wrong on the level, I'm level 4 actually but with 43 stealth, apparently I have +11 stealth on my armor. I had already cleared part of GMS (but not leveled up because right now gaining levels is a pain in the rear, I think that classic mode right now might need an experience buff cause killing mobs nearly give you no XP at all, at least I can't seem to level by killing stuff like I used to, the vast majority of XP I get comes from completing the quests, not sure if it's intended to stiffle leveling this much or just an oversight of the classic system).
Anyway, I wasn't able to reproduce the problem this time. I entered the place and I was able to sneak somewhat closer to them. How you can get so close to them on 44 stealth I have no clue when with 43 getting closer to even the dogs gets me on orange very quickly, but the lunatics this time weren't going auto red immediatly. I remember the past atempt the dog was still barely on yellow and they turned immediatly red, they didn't went through any other colour stages and this is the same character with the same equipment at the same level... I can only assume that this is indeed a bug, but doesn't hits every time. As my luck would have it, I couldn't manage to reproduce it when I was activly trying to get you screenshots.
You do are right, CC is the primary form of defense of my character to be honest. But my CC will only get to work in the first place if I dictate the rules of engagement. This means I have to get into the right position before I iniciate combat! I must be close enough to use my psi abillities. I must be in a place or at least the enemy has to be in a place where I can easily CC a few in a round... Stealth plays a major role in it and it's incredibly hard if not impossible to be able to use my CC if my stealth isn't allowing me to dictate the rules of engagement.
You aren't right that I don't focus on stealth. Agillity is 7, while not my primary stat it is already a good bonus. Of course my primary is will for the psi build. I also have made that character for punching right? He is either 8 or 9 agillity. Also don't forget that I don't divide my points. If I pick a skill I am always going to level that skill up to it's max on every level up, excepting for the biology in which I only care enough to get the doctor feat, then it goes into persuasion.
So while CC might be the form of defense all characters use, I don't think primary would be right, you cannot just says, CC and you die. In a heavy strenght character you can tank damage, that's your primary form of defense until your CC can start to kick in. In a character that uses stealth, stealth is your primary defense until you can get into a position where you are able to beggin the combat by laying down the CC first and foremost... I actually think it was a very poor idea (and that is just my opinion anyway) to make stealth remove all MP. Sure there is interloper to kinda circunvent that, but that is for the people who have the liberty to take it. My character does not, the first skill it needs is marksman to get those stun bolts going at 25-AP and then the psi feats which I very much need start showing up so interloper is again left behind, much like the doctor feat. It's a great feat but really, most characters just do not have the liberty to pick it until much later in the game when nothing else of use for their build is being offered.
Of course the reason I stopped playing again are none of these problems. I was already getting pretty annoyed that I couldn't sell everything I find, heck, not even half! Then comes along GMS where I can't even do the middle and lower section without having to go back to unload my inventory, it was the straw that broke the camel's back. For me anyway.
