Something

set wd=f:\temp
set od=f:\snes
:--------
@echo off
if not exist "%~dp0\7za.exe" (
  echo 7za.exe missing. Place it next to this script and start again.
  pause
  exit
)
for /f "tokens=*" %%i in (
'dir /b /s /a-d "%~1\*.7z"'
) do (
  "%~dp0\7za.exe" e "%%i" -o"%wd%\tempext\"
  if not exist "%od%\%%~pi\" md "%od%\%%~pi\"
    "%~dp0\7za.exe" a -t7z -mx0 -md=6m "%wd%\%%~ni.7z" "%wd%\tempext\*"
    move "%wd%\%%~ni.7z" "%od%\%%~pi\"
  rd /q /s "%wd%\tempext\"
)