honeycomb affordable prosthetic

Looking onto MIT affordable foot design 

and some other attempts to make an adjustable limb, 

 I believe there could be a better, cheaper (less metal, fewer parts), more universal (better adjustable) approach:

Silicon only (or insertable L like springy metallic stem, if not enough)  high boot like shape with a cut to adjust the width and tall enough to cut out the extra hight, with a set of insertable u-like silicon cushions. The Michlin (*typo) like honeycomb structures should be soft and springy enough to mimic natural foot.