I'm not quite sure what would be the best way to add in the Emerald, other than rewriting the scene. If it was added in, there shouldn't be any bugs in the game for owning it.
Frankly, it doesn't sound to me that there would be any good reason to add it. Even if some of the event text would hint at such, you'd still have too much information missing related to it to make the whole insertion a reasonable request for a translation.
Then if I heal my characters up then the weapon is usable again??
What yuka said. If it really works like you said (and your healing didn't include WP/MP restoring), then it sounds interesting.
Perhaps I could write some possibly non-obvious basics about the game, without spoilers:
The game has Weapon Points (WP) and Magic Points (MP). Basic weapon attack is free. Other weapon skills tend to cost WP. All magic tends to cost MP. The WP/MP costs are not directly shown in menus, instead each skill shows how many times it can be used if you spend all your WP/MP using it. All weapon skills are paid from a single pool of WP points. Each magic school has its own pool of MP.
Each individual equipped weapon has a Weapon Level (WL) starting at 0, that gets reset to 0 if you unequip it even once. Each time the WL of an equipped weapon increases, your max WP increases (higher WLs give more increase). For max MP, you just gain it by practise, without further complications.
There are three rows for characters in your party. Most weapon types only work from the front row (they have a range of 1). Spears have a range of 2. Bows have an unlimited range. That covers all basic weapons.
There are four directions from which you can encounter an enemy party. This is where the "Position" option in menu comes to play. It basically lets you choose your formation for all four directions simultaenously
, by letting you assign a position for each character in a 3x3 table. For example, if you place 3 characters out of more than 3 characters in the (screen-wise) rightmost positions, they will be in back row if a frontal attack occurs. If an attack from right side occurs instead, this "back row" will be evenly split into all 3 rows as the Position picture shows. Only the middle-middle character will always be at the same position, regardless of attack direction.
Well, hopefully no one considers these basics as spoilers. There are also various other things, but I don't want to test the limit of what is spoiler and what isn't.
By the way, regarding those cosmetic glitches that disappear quickly..
I hope these glitches are purely cosmetic, with no risk of other effects, because we probably miss a lot of them because they trigger so rarely. Everything else seems to be working so nicely.