Once again: nothing in the rules states that you can only attack with a weapon once per major action.
There are unfortunately a lot of things that the rules don't explicitly state in this edition.
But most of the alternative readings are silly, crazy or down-right game breaking so...
That is not how I interpret the rule.
I wish I could find a clear explicit rule that prevent you from you from firing that single shot weapon 8 times in a single major action, but I can't. So if you wish to rule it like that. then you are free to do that.
But honestly now, do that reading make sense to you...?
An attack is not the same as an action, though an attack can be an action
It take one Major Attack Action to align the weapon on your target and perform one Narrow Burst Attack.
SR5 p. 42 Major Actions - Attack
A character may perform one of a variety of forms of attack with this Major Action.If you wish to align your gun for
second Narrow Burst Attack then you take a
second Major Attack Action. Your first Major Action ended once you released the trigger of that first attack.
If you are wielding
two firearms (one in each hand) then you can align
both of them
at the same time and then perform an attack with each of them
at the same time, in the
same Major Attack Action. This, however, require that you also take a Minor Multiple Attack Action and split the pool between your two attacks.
Once you let go of the trigger of your both weapons the Major Action is considered to be over.
FA allows you to do multiple attacks explicitly without the multiple attack action
Precisely. A regular Full Auto attack include the option to attack multiple targets or the same target more than once. This is within the limit of what you can do with your regular Major Attack Action. Full Auto act as an exception and it let you attack multiple times with a single firearm. But at a cost of 6 AR.
Ruling that you can
also do the
exact same thing with a single shot weapon, but
without a cost of 6 AR, makes
no sense at all(!) That is crazy talk! What would then the purpose of Full Auto be?!
Yes, since there are no explicit rule that describe this you are free to interpret it like that, but I highly doubt that this is how the rule is intended to be read.
If it would make more sense for a rule to be in a rule book, that's fine, but that doesn't change the fact that the rule isn't in that rule book. Using the non-existent rule would be either a house rule or a ruling.
For other editions I would 100% agree with you and if you followed me for the last 10 years or so you would know that I
often used the same arguments you are using... but since they cut so many clarifying (or 'redundant' as they probably saw it) rules and examples you end up with a rule structure in 6e that is far from as strict as it used to be (I wish this wasn't the case, but it is).
In this edition it is not only OK, it is
required, to use common sense (in a
much broader sense than in previous editions).
Who says you have to dual-wield two swords?
SR6 p. 111 Multiple Attacks
...or using a sword in each hand...(ask yourself why they would even mention "a sword in each hand" if the intention really was that you could just as easy do the same amount of attacks while wielding just one sword in one hand, and without off-hand penalties to boot?)
It is common practice in TTRPGs that you get access to more attacks if you wield two weapons compared to if you wield one weapon.
It is also common practice in TTRPGs that your off-hand attack is generally weaker than your main hand attack (unless you are ambidextrous).
All of the above is supported with the reading I am presenting to you.
None of the above is supported if you rule that you can also just do two attacks with the sword you have in your main hand (without off-hand penalties).
You swing your your melee weapon once, and then your Major Attack Action is over.
If you wish to swing your melee weapon a
second time you better have enough Minor Actions to trade in for a
second Major Attack Action.
If you wield
two swords (one in each hand) then you can swing
both of them
at the same time in the
same Major Attack Action (by adding a Minor Multiple Attack Action). Once you swinged your both swords the Major Attack Action is over.
Very streamlined with how firearms attacks would have been resolved. I like this a lot ;-)
Is there anything stopping me from doing two minor actions to ready either Agility or Agility*2 weapons, and then doing a multi-attack with all of them using the minor+major I have left?
Well, Ready Weapon is typically considered a Major Action, but besides that? Nope. You go ahead and rule it like that. No limit. Why should there be, right? Just spend a few turns to ready 200 throwing weapons. And then you anticipate the shit out of all of them. Yes. This seem to be the intended way to resolve this ;-)
Even though it does not explicitly say so it is clearly intended that Agility / 2 act as the limit on the amount of shurikens / throwing knives you are allowed to Ready at the same time and are allowed to throw in one Major Attack Action.
Again. Apply some common sense is not forbidden.
I think you might have a very difficult time playing 6e if you don't start to embrace this mindset when reading the rules.... :-/