I don't want to ruin anyone's fun, but I guess this will need much more thought:

Devs said they were working on trying to fix mudra's lag problem. Until then, it's hard to see your idea working, but once it's done, it could be awesome! Especially with every combination generating a different buff. (ASTs would die of envy)

Mixing real mats in battle can also be a problem. Devs said they would never make Ninjas have Throw because they would need to carry good weapons/gear only to throw away. They even told about the possibility of people in raids making Ninjas throw allagan gear(Now prototype) only to keep high DPS... It would be unfair. Can you imagine people yelling at each other because you've got out of High Elixirs? I can. That's the reason I think Samurai won't have coin toss either, but let's see... They could give it a 'mixing potions' animation, who knows...

As I said, it may require a lot of thinking from the Dev team, but it's not impossible. I really liked the idea and if the next expac brings one more healer, that's one of the jobs I'd like to see implemented. ^.^