I only have two FFXIV accounts, so I can't try this, but maybe someone could.
1) Create several Windows user accounts. Log in with each one to create the profile directory.
2) Copy the FFXIV folder to each profile directory. (e.g. C:\Users\JoeBlow\FFXIV)
3) Hold Shift and Right-Click the launcher in each user folder. Choose to Run As Another User and input the user's Windows credentials.
4) Login to FFXIV normally using the Square Enix credentials.
If that does work, it's super easy to automate with a batch file and PSExec.
1) Create several Windows user accounts. Log in with each one to create the profile directory.
2) Copy the FFXIV folder to each profile directory. (e.g. C:\Users\JoeBlow\FFXIV)
3) Hold Shift and Right-Click the launcher in each user folder. Choose to Run As Another User and input the user's Windows credentials.
4) Login to FFXIV normally using the Square Enix credentials.
If that does work, it's super easy to automate with a batch file and PSExec.