Neither online.exe or psobb.exe process command line parameters to change your character slots.
What online.exe changes is a registry key (HKCU\Software\SonicTeam\PSOBB\Ephinea\CHARACTER_BANK), which is a DWORD.
You could probably make a batch file to do what you want, though, something like:
Code:
regedit.exe /s bank.reg
c:\users\somegoon\EphineaPSO\psobb.exe
Contents of bank.reg would look like so:
Code:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\SonicTeam\PSOBB\Ephinea]
"CHARACTER_BANK"=dword:00000001
You can make multiple bank.reg files with different values for CHARACTER_BANK and have multiple batch files, or you could be fancy and do like this for your batch file (assuming you'll keep your registry files named bank1-bank9.reg or w/e in c:\users\somegoon\documents):
Code:
regedit.exe /s c:\users\somegoon\documents\bank%1.reg
c:\users\somegoon\EphineaPSO\psobb.exe
Then make a shortcut to that batch file and call it like "mybatch.bat 1" or "mybatch.bat 2"... or just call it from the Start Menu "Run" function...
Writing this kind of fast, but hope you understand what I am trying to explain here...
Maybe, some day, we will add command line to do it. =P