Here is an example of what I am working on:
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I'm not sure if this is what many people want (I haven't had time to read through the thread), I am really doing it for my own groups and my goal is to do all the magic items in the DMG.
I think this is the right general direction but I have some criticisms, if you don't mind.
I think it's a bit too standardized in terms of requirements, it's hard to believe every cloak of that nature would be made the exact same way, but if you presented it more as "This is one wizard's blueprint for how she made Displacer Beast cloak", and suggest that the DM feel free to mix it up a bit. An "alternative ingredients" bit might be nice, even you didn't detail how they were used.
I'd also drop the ability checks entirely, because all you're doing is adding a significant chance than an interesting process that effort was put into gets thrown away. And the net effect of that will be one of two things:
1) The players just give up on this stuff. A lot of players will be literally disgusted if they put that much effort in, and a couple of really bad d20 rolls, which are highly random, note, ruined all that effort. I do mean disgusted. People underestimate how big this kind of thing feels to players, especially in the abstract.
2) The players will massively oversupply themselves on the hope that at least one of the attempts succeeds. And then you have a bad situation where it may well be that they get enough for, say 3-5 cloaks, and succeed in making 3-5 cloaks. Suddenly the ENTIRE PARTY has Displacer Beast cloaks. But you're encouraging this situation strongly by including a total failure chance.
Also generally speaking real craftspeople don't just... "fail" at stuff. Like, if I paint a painting, I'm not just going to set it on fire or rip the canvas or whatever. If my mum is making a pair of trousers, she's not just going to cut them in half or the like! If you actually have the proficiency, the failure chance should probably be zero - rolling should be for amateurs. (There are some examples where it does happen - but they're pretty rare and usually either involve unusual materials in a sense beyond this, primadonnas/artistes, or most often - people who aren't actually that skilled that they'd be considered "proficient").
Now I see you're using DC 10 to try and mitigate this a bit. That's cool but all it does is mean that there's a very small chance that the failure will happen, which doesn't really make it interesting or engaging, and I think removing it entirely and making the process more narrative (or about finding people with rare and specialized skills, and/or costing TIME instead, or money, or both on failure would be much more effective. The process itself is what makes it interesting, not any "failure chance".