Add a possibility to link variables (i.e. relations) to mathcad calculation parameters (in and out).
Similiar as it exists for ProE - see
http://www.imakenews.com/ptcexpress/e_article000856292.cfm
So for a given length of a beam and known charge its diameter can be calculated (and automatically modified by driving relation)
Other things might usefull to transfer to/from mathcad:
Density, Transformations, Centroid, Volume of a part/assembly