The first one is easy. Self sufficient, hardy characters, that base their feats (as in acts, not the mechanical feat from PHB) on exceptional stamina/endurance/will power.
I don't think you quite understood where I was going with that. To meet the qualifications for #1, you have to start with a social role.
An example might be, "In the Dango culture, they have this idea of peace keeper which is something like the role of police. But unlike police, the peace keeper isn't expected to oppose evil or criminal behavior with force. Instead, the peace keeper resists criminality passively by simply being an obdurate immovable obstacle. He can't be hurt. He publically shames the criminal, he calls on the criminal to repent, he blocks the criminals way, and when the criminal lashes out and tries to attack him, he simply ignores the attack. If forced to protect himself, he prefers restrained violence to brutality. He sits on the foe and uses his bulk to control the foe. He shoves his enemy with his belly. He jams his foe up against a wall. Being forced to use a weapon on a living foe, or to injure a living foe is considered weakness in the peacekeeper tradition. Only against things completely opposed to life, does the peacekeeper result willingly to force."
And if you do that sort of world building, and you start incorporating related ideas in many different cultures, what you may discover after a while is you've defined an outlook and a social role that no core class suits well. So then you might decide to create a Brick class with a subclasses of "Peacekeeper", "Brute", "Unyielding", and "Juggernaut" based on different ways cultures in your campaign have built on this tradition of guys that can take a hit and laugh it off.
In other words, you are starting with the idea of the class as, "What does this class do when it isn't an adventurer? How do they belong in the community?", and then moving from that toward, "When a player who gains setting mastery wants to make a character of that background, what abilities relevant to adventuring would they have?"
The second one....... i'm not so sure how would the "Brick" work as part of a team. One of the reasons (aside from level progression and resource management) why i posted here actually. I would like more experienced people's (especially with more genre and edition/general RPG savvy) opinions and critical analysis on the subject.
The second one is not based so much, yet, on how the Brick would work as a part of the team, but on how the Brick concept has worked in stories. How they work as part of the team is a balance issue you address in the mechanics of the class. But right now, we haven't got to mechanics. We are still trying to figure out what the mechanics need to represent.
Some examples of Bricks in literature might be The Boy who Couldn't Shudder, The Five Chinese Brothers, Bobby from King of the Hill, Mongo from Blazing Saddles, and the X-Men villains Juggernaut and the Blob. I think your biggest problem in implementing this class idea well is that Consitution is the most passive of the 6 ability scores, and the heroes and villains that are defined by it are defined by their passivity and their inaction. The typically win by doing nothing until their enemy just exhausts themselves or frustrates themselves into a self-destructive tantrum. Indeed, that may indicate that causing foes to have self-destructive tantrums might need to be part of the Bricks suite of powers, at least in some subclasses.
A typical story of this form will have the hero be unaware that anyone is trying to harm him. The villain gives him a cup of poison, which he drains in a single draught and asks for more. After the sixth cup he declares that it is the sweetest wine he's ever been offered. He goes to bed, and the villain attacks him in the dark with axes. But in the morning the hero wakes up, stretches and says that he's never had a more restful sleep, and further that he dreamed he was given a fine massage in the night that has cured him of back pain. And so on and so forth, until in terror the villain runs away or yields, or becomes so enraged that he stamps his foot through the floor and falls into hell, or tears his beard so hard that he tears himself in half.
You don't actually
need a brick class until someone comes to you with a story like that, and says, "I want to play this character.", or if you want to have characters like that in your setting.
Hmm..... working as a subclass of a fighter might actually work.
To be honest, I think it would probably work better than making a brick class because "tough fighter" is probably the character most players will be thinking of when they imagine being a brick. They won't be thinking of a character that solves problems by being simply passively obdurate. They'll want a character that can be bash things while shrugging off most blows, which isn't necessarily at the core of what being a "brick" is actually about as a concept distinct and separate from "Fighter". The vast majority of tough guys in fiction are simply tough fighters.