Something that's come to mind for me is the sheer amount of ingredients for alchemy recipes, and how they follow certain themes for different pieces. On top of that, it seems that, at random intervals, some equipment gets extra effects (for example, I have a Cold Iron Carver with a Moderate Damage Bonus to Beasts). While this is, I imagine, an occurrence that's supposed to be rare, it seems kind of unfair to those who either have not the time to devote to grinding for crowns to buy energy or have not the money to buy it, because this is something that encourages folks to repeatedly make heavy use of the alchemy so as to get that special something.
What I propose is that, so as to not only make getting extras more viable of an ambition to others, but also to increase the variety of options available for them as well, the ability to tweak recipes should be allowed. I don't mean that they should be able to make the items with less ingredients, but that they can add extra ingredients when they make it, either increasing chances to acquire the random enhancements or adding new effects to the item as well.
As an example, take a look at the Valkyrie Mail. It takes twenty Light Shards, five Brimstones, four Owlite Feathers, three Fine Fabrics, two Trojan Horseshoes, and one Sun Silver. While it is indeed great armor, it has a glaring weakness in the extra chance to be set on fire. To help lessen that blow, the one who opts to alchemize the armor could add a piece or two of Volcanic Iron, or maybe Flame Souls, on top of what's already required. The more that's being poured into it, the better the final product.
On the other hand, the knight making the mail would rather add another defensive ability to it, rather than try and reduce the penalties. They then decide to add a Royal Core, which would add a chunk of Piercing resistance to the armor's normal defenses.
However, this does raise the issue of interfering with balance, and for that, limits should be put in place. First and foremost, one can only add up to ten stars' worth of extra ingredients to the formula. This helps prevent abuse by those who happen to have more crowns than anyone else. On top of that, for any additional ingredients to have an effect, the material must be at least as high of a level in stars as the finished product would, therefore one could only add five-star materials when making a Divine Avenger, Heavenly Iron Helmet, Volcanic Pepperbox, or at least a three-star ingredient when making things such as a Surge Breaker Shield, a Graviton Charge, and so forth. The level of both the item and the added material will affect just how much change there is to the original item, the added material being the base used for a formula in determining the effectiveness, while the the created item dictates the maximum amount of adjustment.
This is, of course, a very rough and incomplete idea that would have to be ironed out very, very thoroughly before it could be implemented, deciding things on like what affects what and how, and whether or not there is any compatibility between the item and the material. It would add complexity and variety to the equipment when it's made, eliminate some of the thingsone could only achieve through luck, and would likely inspire people to try and find different combinations for different items, thereby making things fresh and interesting.
Thoughts are welcome, even if I can't read them from over the Internet, so I would prefer some comments instead. All I ask is that it is kept civil.
I think your balancing limits should be more severe.