After someone asked on c.l.l I spent a day on making a defparameter a Cell. The test worked but then I think I tried it live and it failed and I decided I better get back to work on Algebra (but apparently never took it out of my LPR).
while making a clet in computed-class i've also played with the idea of a cell in a defparameter, but i couldn't come up with anything without symbol-macrolet. i think that can't be done transparently with standard common lisp constructs.