I'm not sure how technically possible this is, but I would like to see combinations and recipes create products that have properties falling on a continuum. For example, a material could have a certain amount of hardness based on the amount of ingredient included or how long it was heated, etc. There could even be a tradeoff perhaps, it could be both harder and more brittle.

This would make it such that the exact recipes matter even after everyone has done all the combinations because you may want a different mix of properties depending on the need. However, this doesn't achieve the same kind of progress gating that can be done with unlocking recipes so that may need to also happen on top of a system like this.

Why not a hybrid as you both have suggested? Something like what they describe with the construction of a building?

You start with a Recipe Unlock where you are able to create an item once you have the skill to do so. (Like you said, Combo would just have people looking up recipes anyway.) That doesn't mean you can do it well, and there may even be a chance of failure that diminishes as you improve in that skill. If materials have varying qualities then you can add in the experimentation of a Combo Unlock by swapping out different types of the same general material.

For example you could learn how to make a sword once your skill reaches the right level. At that point it says to use a metal ingot but then you get to decide what type of metal ingot and can create swords of various strengths by using different ones. Even then, ingots of the same type might have different qualities based on how they were made.

It all depends on what attributes materials will have and how they allow us to tweak with them.

The main problem i see with unlocking recipes when you are the right level is that your basically told what you can make and there is no room for discovery.

In CoE technology advances and biomes produce different things, but the progression tree (Apprentice, Journeyman, etc) is only one route, so when one person discovers a new technology that is recipe based, then it unlocks for everyone who is the right skill level.

While it invites wiki lookup, i'm swaying towards Ingredient Unlocks as the main way of doing it, but like Death said on the Q&A about what decides quality, is it crafter or materials.... i think having a 3rd thing in the mix of "how well do you know the recipe" would be good.... this way even if you wiki lookup the recipe and you have perfect materials and your a perfect crafter, it doesn't mean your going to be great at making something for the first time ever.... it might be of a reasonable standard, but it's not going to be perfect without practice.

So a system of...

Recipe > Materials > Crafter > Practice

...might work. Drawback is it invites people to google how to make stuff, but bonus is that no one is going to make anything of a decent quality until they practice how to make it.

I would expect combo, but the combo would need to be one you have the skill and existing knowledge to make to be able to discover it.

And with the patent system in place I wouldn't expect people to post much in the way of recipes. There is a lot of cash available to those that know and discover recipes first.

From the bits and pieces we've heard so far, I would like to see a hybrid system that works as follows.

Crafting would be recipe based. You would not automatically learn new recipes when you level, they would need to be bought, learned from a teacher, etc.

Recipes would allow for individual variation. For example, a sword needs a blade, guard, and hilt. You could have a variety of detailed recipes for each component, each requiring different materials and levels of skill. Then you could have a recipe for putting the sword together that allows you to use any of those components as long as you have 1 blade, 1 guard, and 1 hilt. Many recipes could be broken down this way. When baking bread and pastries you would have different combinations of wet ingredients, dry ingredients, and rising agents. An option for additions of fruit and nuts, or a frosting on top. As long as the proportions are correct, and you use the correct category of ingredient, the individual ingredients matter much less. Recipes for books, clothing, pottery, herbal teas, medicines, massage oils etc. could all be broken down this way.

Another consideration for crafting is that some will be preferred over others based on the biome you live in. This will be either because the finished project has advantages in that biome, or because the materials needed are more accessible so the finished product is cheaper than a product using imported materials. So even if they go for an entirely Combo Unlock system, there will be useful recipe variations in the game.

Good point about the modularity of weapons. Just because you learn how to make a sword that doesn't mean you know how to make all versions of a sword. There could be dozens of cross guard types, blade types, handle types, etc....and knowing the combo of materials needed to crate it doesn't mean your character knows how to make that exact shape or pattern just by looking up the materials needed online.

I'd personally see it a similar way to how housing is planned to be built.

1) Have recipes, but those recipes are basically just a guideline to reach an overall result. For example, root A grinded to powder with plant B equals healing poultice. What strength and attributes that healing poultice would have, no idea yet, but you know the end result would be something akin to an healing poultice. That would essentially be the "foundation" of your alchemic creation.

2) Have each individual potential alchemic ingredient give different effects to the creations they're used in, depending on how they're used. For example, bark C is used inside the aforementioned creation, when grinded to a powder with a mortar & pestle it increases cauterization, but when distilled using an alembic it instead decreases blood loss. However, if reduced to ashes, it might instead increase blood loss, an effect you would likely not want to have. This is where experimentation comes into play and where some very interesting combinations could burst forth, or where side-effects could show up. Basically, adding or modifying to an existing recipe would have the same kind of effect as building a house in wood (flammability, vulnerable to sieges, low cost, etc.) versus building your house in stone (resistant to impacts & weather, long-term durability, costly, etc.); they're still both houses, but the materials used change completely how they behave.

This system doesn't necessarily ensures everything remains secret and no one share interesting information on internet or stuff like that, but it does ensure quite a few interesting things from a gameplay perspective :

It firstly ensures that alchemy has a very strong differentiation between every region it is used into; an healing poultice from the village in a specific forest could be immensely powerful at stopping blood loss, but it could skip cauterization entirely and make it so the user still requires medical attention afterward, whereas another poultice from elsewhere could be a more end-all-treat-all solution to most basic forms of external injuries but an incredibly painful burning sensation could prevent anyone using it from fighting for a moment. This would create regional differences between the same recipes and most importantly, as a result, it would foster trade and economic ventures with not only the alchemic ingredients but also the finished products, the potions, themselves.

Second, this system also brings some extent of secrecy and unknown to the more rare ingredients out there. Say for instance a lich's phylactery could be considered an ingredient in alchemy, something so rare would obviously not have been experimented upon that much in the past and, as a result, it means pretty much nothing is known about its effect in specific potion types. This very fact pretty much means it opens room for legendary ingredients to exist and for legendary potions, created using such ingredients, to exist too, and more importantly than one such potion would most likely end up completely different from another legendary potion someone else made, even if the ingredient itself might've been the exact same. Even in more mundane play, a rare ingredient, a simple plant or something only found in one or two biomes, could end with major impacts on the overall game. Take for example a type of cactus only found in the arid deserts, and a kingdom, on that server, has a monopoly on all the arid deserts located on the server. Such a kingdom could very well decide that unique cactus is now to be used only by the military for warfare purposes, and use or trade outside of that is strictly forbidden. This leads to military secrets, to a kingdom having a potential ace in the hole for warfare, to black markets and smuggling rings for that item, to enemies paying the high price in exchange for experimentation information on that ingredient, etc.

Finally, it also sits very well with the already-planned research & technology system CoE plans to have. Everything mentioned in point 1) could be subject to such research (for example, to discover a brand-new recipe for a new type of item, or to discover substitute primary ingredients for an already-existing recipe), and everything in point 2) could still stand firmly above such research endeavors as the way to customize those further.