Alchemical Fusion

I like this alchemy fusion, though I'd personally be satisfied with having an alchemy system similar to what the recent Dragon Quest games have. It's rather simple and, for Bloodstained, may pretty much be the only means to earn some of the equipment in the game. This can work if the said equipment have unusual quirks, such as a particular suit of armor where instead of just having high defense, the armor will have an outrageously high evasion buff with the trade-off of a mediocre defense rating. Alchemy must be part of Bloodstained whether it's a relatively simple kind of alchemy or one that can be able to just augment certain characteristics of equipped weapons/armor/items.

And it might count as getting that PSN trophy / XBox achievement / Nintendo accomplishment for obtaining all armor in Bloodstained!

I'll be honest: the main purpose for my suggestion was to be able to carry a weapon you like throughout the game without it becoming obsolete while still making item hunts useful.

If you go with a normal upgrade system, you will almost always end up in a situation where it is straight up better either to exclusively upgrade an item or to ignore the upgrade system altogether in favor of picking up new equipment that outclasses it. With a system that fuses two items, you change the conversation from "which will give you better stats," in which there is a clear objective winner to "which do I like the look of, and which one does a cool thing I like," which is far more preference based, allowing for customization and upgrades without regret.

At its base concept, this is similar to the transmogrification feature in World of Warcraft, which allows you to make a piece of armor look like another for aesthetic purposes. At this level, it's pretty easy to implement, as you are simply appending the stats from one weapon to another. No change in animation, physics, or anything else other than straight numbers.

The more advanced version I mentioned - mixing and matching elemental attributes and special abilities - could be trickier since it would mean appending visual effects to weapons and possibly altering animations. For sanity's sake, I'd say that it would be best to restrict that sort of customization to weapons of the same type. Otherwise the workload on the animators would explode.

i get you, and the first option you mention is a value callback to change the weapon model, hitbox and animation played when you swing your 'custom' weapon

where the custom weapons i outlined would really shine is in ng+, where people have already beat the game a couple of times and have a bunch of items sitting in their inventory are now messing around seeing how deep they can go, you would be fairly limited on the 1st playthrough due to powerful weapons being in limited numbers and the amount of grind you would need to overpower a single weapon like you say if its properly balanced (like a weapon/armors att/def value only adds 1/4 to 1/8 of its full value when used for mats or such but gaining the full stat bumps, the debuff mats would also allow you to scale back a weapon should you decide youve made something too powerful but dont want to start over or youre going for a specific build like above), and the 2nd playthrough youd be playing around and likely making quite a few different weapons and just starting to get the hang of it

the method i pointed out above would actually not require a ton of work, maybe 1-3 extra tables of values like weapon appearance call values (likely already to be in the game as part of the weapon database), custom weapon table (appended to the end of the weapon database or part of a separate database depends on coding preferences and how secure the standard weapons can be made against overwrites), and temper database (basically a compilation of certain columns from the weapon and armor databases to make value callbacks easier), some coding to make the databases pull references and alter values correctly, and taking the color customization that will already be implemented for miriam and extending it to weapons (so no extra animation, just repurposing some features and assets that are already there ^_^)

On the other hand, there's a segment of players that either grow attached to a certain look for their character or actively dislike the look of equipment that is in other respects an upgrade.  The primary point of my suggestion - and the entire point of the WoW Transmogrify system - is that the desire for a certain appearance and the desire for more effective equipment don't have to be at odds.  Loot would still be important in the system I outlined.   You would just have the option of keeping the appearance of a weapon you've come to consider part of your character's identification.

The other point is that sometimes you get a weapon with an ability you like that has no high-powered analogues.  Take for example, the whip sword in Aria of Sorrow.  It was a nice weapon with the best reach in its class of weapons.  There are other weapons you get later on that also have nice features, but if you happened to like that one, you're kind of out luck later on in the game.  This would be a way around that, meaning that you have to make decisions on more criteria than just numerical superiority.

As for WoW, it more or less just lets you use the model for any equipment you own for the appearance of any other equipment of the same type you own.  It's a vanity feature, and one of the more popular additions to WoW(and an often requested feature in other MMOs)

Oh this is specifically about aesthetics? Ok I think I understand you better now. I don't expect many weapons found in the early or midpoint of the game to have much aesthetic appeal and the sorts of weapons that likely will are probably decently rare/powerful weapons you find later with like specialty names (i.e. the "Masamune"). I expect there to be a wide range of weapons at different strengths in each class. For base weapons you also have to account for balance. I expect most weapons with great range to have less power and vice versa - that's what happened with that Whip-Sword (of course the version in Bloodstained is likely to be extremely good). I dunno, I don't think this is a big deal because I don't expect there to not be a weapon type you can take with you to higher levels and the trade-off between something look cool/pretty and being strong seem valuable to have? I'm also skeptical about how much distinction there will be in the visualization of weapons or armor (aside from designated costumes) but I guess we will see soon enough. I dunno, I can respect your position but it just seems a bit unnecessary to me.