Not just the command field!
The real problem was that all the parameters (e.g. NPROC) were not stored in
the kernel anywhere, so if you wanted to have one copy of the 'ps' binary
which would work on two different machines (but which were running the same
version of the kernel)... rotsa ruck.
I've hacked my copy of 'ps' to grovel around in the system's symbol table,
and print 'wchan' symbolically.