You don't need custom. There are a full range of lengths and angles available.
I custom fitted my bike myself--makes me feel like I got the Lance Armstrong treatment. I'm pretty well convinced that you'd have to actually clone me to produce another human being who would be so perfectly comfortable and perform at the optimum on my bike.
As for the cranks. I replaced the standard 175mm length cranks with Shimano XT 172.5mm cranks. Trust me, you don't need anything with a finer difference than 2.5mm. I've heard that people can't find such sizes here--I bought mine in Japan--but I swear they do exist. I'm a big fan of special ordering at my LBS.
Stems too come in a fantastic wealth of angles and lengths. Outside of velodrome racing and maybe time trialing on the road, there's no reason you should have to have parts custom made just for you. Frames are custom made, parts just come in different specs.