TOPIC:

placing a measure on the human effort about the login, a click to close the login window and a click to hit "Token login" is the same, theoretically, because in practice one is harder due the size of buttons.

But putting aside the philosophical issues, there's some possible ways to follow, some easier than other so, let me spread what comes to my mind:
1 - Create a setting (on/off) to player chose if want an Automatic token login when entering our servers, not opening that Token Login Window;
2 - Change plugins to show a window to player when entered with a registered nickname and didn't logged in (with a timer, similar to when's renamed to Unregistered***). Won't work if players join with any other nickname;
3 - Similar as point 2) but on BTPro client side. Looks the logical solution but, I can't see (now) a way to the client know if a Login was successful (or not);

Can be other options (discussion is open) and all have good and bad sides. In my opinion it's a choice with low benefits compared with the work coding it. And the reason is: When a player "close the box Token login tool box by an accident" means that he recognize the "misclick", being easy to login after via Client list in couple seconds. As I said, problem solved (imo, not even a problem ^^). If a player don't login when he joins, it's his choice. And I think is not that hard hit the Token Login button ^^

Anyway, it's my opinion