The Blade Works is a pretty cool concept. Archer's version has giant cogs floating in the sky as it depicts that he is moving forward without remembering why, whereas Shirou's has a pristine sky with no fog at all. According to the stuff I have researched on this topic, Shirou's 'alignment' is Sword rather than any other element, and so is his 'origin,' which allows for the casting of the Blade Works and prevents him from being good with other elements as they aren't in his natural affinity. I theorize that being almost dead and having Excalibur's Sheath put into him, then living for many years with it, forced those attributes to change.
The Blade Works seems conditional. He can not actually invoke The Blade Works with his current output of mana, as though he has 24 Circuits (I think the average Magus has 20), he has absolute shit for their use as he hasn't really been using them at all.
The true power of The Blade Works is not that it makes swords. It is that it creates
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. Conceptual Weapons are entirely different than projection. A projected weapon will be destroyed shortly after its creation since it tries to act like it should exist but the world knows better, and destroys it so that the paradox is gone. A Conceptual Weapon however is something the world does not destroy on its own, and can have incredible effects. Excalibur's Sheath is considered a Conceptual Weapon. The key ability of The Blade Works is that whereas a Magus could probably project let's say, Gae Bolg or Rule Breaker, it would be entirely unable to use any special abilities and shatter incredibly fast. Shirou however, could in theory activate Gae Bolg or sever contracts and such with Rule Breaker. The Blade Works is where they are 'prepared' and he casts them out by 'drawing them from the Blade Works.'
In other words, The Blade Works is Shirou's mind, and his true power is being able to literally create what his mind perceives and use it. The underlying condition above all however is that his 'Element' is Sword and his 'Origin' is Sword. In the Heaven's Feel route, Shirou chooses to save one person over the world. Therefore, he abandons his Origin, and the casting of the Blade Works is now impossible to fully invoke.
The Blade Works is technically always active, and the Reality Marble 'casts his mind out and eats away at reality.' The casting of the Blade Works tosses the enemy into the armory rather than having to draw each weapon from said armory. There is no strain or need to limit himself by drawing only a certain amount of swords at once (which is very limited unless he's linked to a huge ass mana source, like wanna-be power reactor Tohsaka's 40 natural Magic Circuits).