I like the use of right mouse for an input trigger, it's nice to separate the alchemy input between the two hands. That being said, I'm not really a fan of this idea overall. It would get tiring to have to draw out your mixture every time, it's a more strenuous action than just pressing a few keys. This goes without mentioning how much slower it is overall.
The fact this is a twin-stick makes me question the input logistics. What happens to the cursor during and after entering the radial menu? Is the menu always kept centered somewhere, or is does it appear relative to the cursor? If so, what if the cursor is somewhere that makes part of the menu go out of bounds? If not, what happens to the player's aim after the alchemy input inevitably changes their final cursor position? It sounds tricky to me.
I wouldn't be against a cosmetic wheel that shows you button prompts and whatnot, but that's just the current mapping with extra steps...