Well.... I think the easiest way will be to start from the "FHIST" compset (which sets up time-varying forcing). Then you'd need to change the way that the SST/ice file is specified.
I think you would want to provide the file using the parameter SSTICE_DATA_FILENAME in env_run.xml. That should point to the monthly climatology you want, and then you would need to adjust things to basically mimic the F2000climo setup:
SSTICE_YEAR_ALIGN = 1
SSTICE_YEAR_START = 0
SSTICE_YEAR_END = 0
I think you will need to make sure that the time coordinate of your climatology looks like it is just year 0, as in this example file:
/glade/p/cesmdata/inputdata/atm/cam/sst/sst_HadOIBl_bc_1x1_2000climo_c180511.nc
One issue you might encounter is that the default data sets for other forcings (e.g., CO2, aerosol emissions) end in 2014. You will need to decide how to deal with those forcings.
