https://www.wowhead.com/news/the-new-draconic-phial-cauldron-coming-in-patch-10-1-331980

So, a quick overview:

• The cauldron is BoP and requires alchemy to use.
• It lets you pick which phial you want, but you can only pick phial with recipes that are known by the alchemist that placed it.
• Phials are not part of the ingredients to make it.

I believe this will mean that alchemist alts will become largely pointless, since they won't be able to supply cauldrons to the raid (you need an alchemist with all of the actual recipes in the raid), and the phials they make can't be used to make cauldrons, either.

Really hoping that Blizzard reconsiders. Off the top of my head, I'd probably say to make the recipe require some amount of each phial (or maybe have a few different recipes like the feasts), make the cauldron not require alchemy to use, and make it so that it always lets you pick any flask instead of needing to know the recipes.