This can be done piecemeal: make platform HALs respect the VV COMM set baud rate command (return 1 if so, otherwise the call already returns 0). Move platform console/debug channel baud rate options to common HAL, let diag_init / claim_comms call the channel driver to set the baud rate as requested.
Gary already did this for the iPAQ (IIRC).
This bug has moved to http://bugs.ecos.sourceware.org/show_bug.cgi?id=26808