Thanks to an observation by Chris on the Swapmeet Forums, a working solution for the physics parameter problems has been found. To use special physics parameters--constraints, motors, and springs--in a dynamic fashion, simply store them in strings rather than their custom counterpart. If you're using arrays, make sure to set the column type to parameter and the parameter to string (don't use the string column type).
Aside from that simple caveat, everything else works. Check out this simple test for an example; left click to break springs, space to set them as long. The source CMO is available, as always.
http://devlab.flashbangstudios.biz/article.php?story=20040624154615413