I think I just wanted to namedrop "auxin"  The first time I saw the skeletal notation for IAA, I was amazed at what a cousin it was, I mean, it must be that these indoles are what our friends are making tryptophan, etc., from, no?  But anyways...   Setting aside the actual kinetics for a moment, it would be fairly simple to make a try at something like this wouldn't it?  Micropropagation?  Liquid cell suspension?  What do you think our ideal nutrient medium would look like here? 

Whitebread420 already made the point above that the whole thread is pretty silly considering that plants already do all of this anyways without any need for mucking about.  But the thing is, if a liquid cell suspension could be achieved, and some sort of simple bioreactor imagined, we'd at least be getting more in the ball park of being able to sway towards substitutions most desired by substrates introduced, don't you think?  Ultrafiltraters are already in range of a hundred dollars or so... 

But then I'll be damned if the greatest thing still wouldn't be having each enzyme on its own (and by the GRAM!)...  I can't believe it's 1000s and 1000s of dollars for mere micrograms of these things...  And have you read about this stuff?  Where enzymes are immobilized actively into PVP mesh-arrays, and the substrate can simply be "pumped through" this mesh while desired product comes out the other end?   It really is something to dream on for someone with all the aspirations of an organic chemist, but without the stomach for monkeying with "sodium cyanoborohydride."

EDIT: Benzyme, you've made it quite clear how impractical enzyme expression is outside the lab...  But why is it that in most fancy labs today they don't use enzymes in the way we're talking about here for syntheses?  Why isn't every million dollar lab doing enzyme catalyzed reactions along these lines already?  I mean, couldn't they replicate these things by kilogram and streamline so many other costs of research/production?