Whilst I'm not a figure modeller, before you get to far along the way, there's a few reasons that I can give that the figures printed in Shapeways stainless steel (+variants) might not reach your expectations.
The detail is not fine enough, you might come up against issue of thin walls and the texture of the printed stainless is quite irregular, see the Stainless Steel Design Guidelines for more info (the image attached to 'Weave in thicker walls to support thinner walls' was attacked with a Dremel - the untouched print can be seen here)
I'd like to iterate that I'm not jooking for amazing amounts detail. They are only going to be 4cm in height, and I'm only interested in making these figures in metal. I did research on the metal design guidelines before I decided I wanted to do this.
I have sent a PM as we do a huge amount of character models. An example is attached. If you are dead set on the metals then at 4cm we think its possible to get some quite nice models made. Details will be limited to 1mm but even still it can look very nice.