The sentence rings false in my head. Clearly this is because "weapons" is a countable noun, and "armor" is an uncountable noun. So one could fix this sentence by breaking it up into two clauses (e.g. "So many weapons, and so much armor!"), or by replacing a countable noun with an uncountable one (e.g. "So much armor and weaponry!"). But barring those two types of drastic changes, can anything be done to fix this sentence? Is there any way to properly modify a sentence with an uncountable noun and a countable noun appended together?
How to join a countable noun with an uncountable one in one sentence, while expressing that one is "so many" while the other is "so much"?
The easiest solution would be to use the conjunction, and, to connect the two clauses together; however, the OP believes this would drastically change the sentiment of the original sentence. So I would like to suggest a few possible alternatives; my first is to use the adjective more, which can be used with both mass and count nouns.
We have more weapons and armour than we could dream of.
The forge chimneys billowed smoke day and night as the weapon smiths forged more armour and weapons, fed by a steady stream of ore now coming from the Midean Mountains and the peaks coldwards of Parmia.
Then they mustered full-size armies under consular commanders only to have these just as thoroughly trounced by Spartacus, who with each victory captured more weapons and armour to equip his forces
My second suggestion is to use quantities of or amount of. Quantity can be used for both singular and plural nouns but preferably for inanimate ones. The standard rule says to reserve amount for nouns that can be measured in bulk and are uncountable. But I found instances where this "rule" was not always followed.
Vast quantities of armour and weapons were also obtained, including hundreds of two-handed and heavy swords...
...18,300 lb of silver in bullion and in coin, a large number of silver vases and quantities of copper and iron, besides a vast amount of munitions, armour and weapons
But while the central armouries produced a considerable amount of weapons and armour
A tremendous amount of armour and weapons had been sent into the region to strengthen the military that were doing battle against the invading army.
However, on most occasions armies went into battle with large quantities of traditional weapons and armour.
... where staggering quantities of armour and weapons were buried, probably representing hundreds of warriors either killed or captured.
There's always the simpler fix: since one is a countable and the other is not, qualify them separately:
So many weapons and so much armor!