Potion expansion: Cauldron

A cauldron placed onto a campfire could expand the traditional brewing system. Adding sulfur to the campfire could add a blue glow and reflect the use of blaze powder in brewing stands.

[edit, I removed my suggestion of mixed potions since it might not make much sense.]

Adding three potions with the same effect into a cauldron could result in a concentration. A concentration is a more potent version; the potency depends on dust used in the potion. That is, glowstone or redstone. Making a potion longer or stronger. A concentration can only be one effect, and visually looks the same, only slightly darker. However, the concentrations are unstable, and slightly harm the player upon consumption.

And I think potions should stack, like at least to three, eight, or sixteen.

Finally: New potion effects: Armadillo scute (or armadillo scute dog armor, similar to turtle shell helmet for turtle master potion; or shulker shells) for resistance potion (super useful, and could be a resistance potion without the slowness of turtle master but less resistance); maybe wither roses for decay potions; honeycomb (or gilded honeycomb) for haste; and weakness could also make mobs take more damage as well as being weaker, like Minecraft Dungeons weakness gong artifact.