I was thinking about this. And i have a solution. You can do some magic with the logOff URL https://login.eveonline.com/Account/LogOff
By specifying a ReturnUrl query param you can redirect the user to your login page after first logging them out.
Like so:
However, i would wrap this usage in some conditional logic, as it would be quite annoying if the user is wanting to auth characters on the same account and has to log in every time to do so.
Enjoy!