3D Modelling

Here's what i would like to do...

I'm a chiropodist (like a podiatrist) - am
involved in the manufacture of custom foot
orthoses (supports) - the current process is to
take a plaster of paris bandage/cast the foot
in the orientation you want(to obtain negative cast)/fill this cast with plaster(to obtain the positive model)/modify the model by adding plaster to various areas to achieve the
correction desired/vacuum mold a heated plastic
blank over the modified plaster model/grind and
finish the support

The way i see it, there are several areas that
a scanner/cnc mill could be involved - what i would like to do is scan the foot(or cast of
the foot)/modify the image on the computer(this
is where having a computer's accuracy and
repeatability would be most beneficial i think)/
then mill the positive cast/finish in the normal
manner

the mill could just produce the orthosis, but, due
to the nature of some of the materials (ie carbon
graphite, etc) it would be much more practical to
mill the positive cast, then use it to make the
orthosis in the traditional way

any info or links or direction would be greatly
appreciated

Chris Ellacott