Sorry for the cross-post, but this question is relevent to both the slime-devel and cmucl-imp lists.
I used Symbolics Lisp Machines for many years and found it very useful when in the debugger to be able to edit and recompile a function and then restart the call to the function (restart-frame).
Is there any chance that SLIME:RESTART-FRAME will be implemented for CMUCL? I guess I do not know the limitations of the CMUCL stack frames and whether this is possible.