On Abstract Damage
under no circumstances should you be able to damage the armor wearer unless the attack is made at a not armored part of the body.
Vampire, like many RPGs uses an abstract damage system. This means that a single attack/defense/damage/soak series of rolls represents a much more complex series of actions than a single strike and parry.
For example:
You stab at him with your knife, but he ducks and grabs your knife arm. You continue to push the knife towards him, matching your force against his, but he's able to gradually twist your arm away from him. You break the stalemate with a swift knee to the gut. As he doubles over, you drive your knife into the unprotected area behind his armpit.
In system terms, most of the time, a scene like this is handled with a simple roll.
Specifically, most of the time, the location you hit someone is unspecified. So unless the armor wearer is literally encased in a magical form of flexible steel, there are going to be chinks and other weak spots that can be exploited.
Better armor has fewer chinks, which is represented with a higher armor rating. This makes it more difficult to damage someone wearing the armor, but not impossible. This is why damage rolls are less likely to inflict damage on someone wearing good armor, but damage can still be inflicted.
On Bricks
The key flaw to your argument is that combat in the dark ages is rarely going to be about plastic vs. bricks, or steel vs. bricks. It's almost always going to be steel on steel. At that point, the important aspects are force, angle of attacks, and the shape of the weapons involved (a slash is much less likely to pierce chain mail than a thrust is).
Even when it's steel vs. wood, or steel vs. iron, combat training is all about controlling the angles of impact. A steel sword doesn't immediately sunder a wooden shield because of the angles of deflection involved.
There's also the bludgeoning issue: A mace might not actually break a helmet, but that doesn't mean your brain hasn't just been scrambled.
On House Rules
The main issue I see with your rule is that it breaks down into two scenarios:
The weapon is inadequate to pierce the armor, in which case the armor wearer is invulnerable.
The weapon is adequate to pierce the armor, in which case the armor degrades severely in combat.
The first issue causes severe gameplay problems. Invulnerable PCs make combat a foregone conclusion (you will win, given enough grinding). Invulnerable NPCs make for comedic and frustrating fights (well, we can't hurt him, but we can mess with him until we get bored).
The second can start to make armor feel disposable. If your armor is torn to ribbons every third fight, it doesn't feel very durable.
Were I wanting to add more emphasis to armor, I'd do it this way:
Move most of the damage levels from the character to the armor. Characters without armor die very quickly.
Damaged armor provides less protection over time, making it more likely that the character dies. However, penalties start very minor / progress slowly at low levels.
Damaged armor below a certain threshold is repaired simply by removing it, performing basic maintenance, and reequiping it. Only serious damage requires repair. Destruction is either unheard of, or only happens after massive damage.
On Armor in Other Systems
Other systems take a different tactic: If the character is damaged, then that must mean the attacker damaged the armor in some way. Whenever the character takes damage, damage/degrade the armor.
Page 79 of V20 clearly states the numbers that you are looking for in a text box called "Advancing New Characters":
Advancing New Characters
Storytellers may choose to allow players to create more experienced and knowledgeable characters. Indeed, players of Vampire: The Masquerade 20th Anniversary Edition may prefer an “ancilla game” or an all-elders chronicle instead. In this case, we recommend first building a neonate character and then granting players a number of experience points that allows them to increase their characters’ Traits to levels suitable to the chronicle and the age of their vampires.
As a basic rule of thumb, “idle” Kindred should have a number of Discipline dots equal to the square root of her age. Remember that players’ characters are rarely “idle” like Storyteller characters, so they’ll rapidly outpace this guideline. That’s fine; they’re out there in the world, having exciting encounters and earning more experience than passive Storyteller characters. Remember that the cost for raising a Trait which is already advanced can be very expensive.
See p. 124 for more information on spending experience points.
Kindred Age Category: Experience Points
Neonate: 0-35
Ancilla: 75-220
Elder: 250-600
Methuselahs: 1000+
I would think of this "rule of thumb" as just a limit of how many disciplines may be bought with XP. For example, if a typical Camarilla fledgling generates with 3 disciplines (up to 5), let's say that he has spent 80 years as an "idle" vampire and has 150 bonus XP. He could theoretically buy a lot of discipline points with that! But is limited to a square root of his age, which is ~9. And he may only buy up to 6, as he already has 3 that he got during generation.
If the Storyteller assumes that the character was not "idle" but rather as active as typical player character during that time, the Storyteller is free do provide bonus XP and no limit on discipline dots.
Best Answer
I do not know if there exist rules for elder Kuei-Jin chargen. So I'll try to summarize the Kin-jin (Kindred) rules.
This one is from Dark Ages: Vampire which, methinks, has the latest incarnation of downtime maturation rules.
The basic idea is that in downtime characters are much less active than when blood flows freely.
Characters get Maturation points based on the time spent in any given downtime period, as below.
Maturation Points (MPs) may be spent at basically the same rates as XPs. But for elder vampires (above 200 years), XP costs increase (but MP costs don't).
It is very complicated, and is even more so as Maturation Point gains and costs depend on the character's activity level in any given century/decade. You should check out the Dark Ages: Storyteller's Companion, pp. 69-75.
If you want less complexity, you can design elders from scratch as you would a neonate, just with more points. The rules are also in the same book, on pp. 75-77. Summary is as follows:
Now, as to the Kuei-Jin, you may proceed with the XP-MP method, which is quite straightforward, as XP is XP in both on the East and the West side.
If you go with the chargen-build method, Attributes, Abilities, Backgrounds and freebies should be as above for Kindred, and I'd give 7 free dots in Disciplines, 6 for Chi Virtues and 2 for Soul Virtues (and the free basic dots as for young characters). And then spend the truckload of freebies as per the KotE core book. I checked some elder Kuei-Jin NPCs in the Tokyo and Hong Kong books, and their freebie levels (very approximative) seem to take them to the upper echelons of their corresponding dharmic age ranges.