First of all, black lists are always a bad idea.

Then you say, those player didn't return to the site. So there is no impact on that player.

And now you can have password protected league for you and your elitist friends


Anyway, there is no such thing as "ruining somebody league" because of it, it just sits there in your (wait) games list.
You will win that month or two later, no big deal.


What I would suggest
1) Reduce move timeout!
1 day is good for play-by-email style games.
1 hour is even better for modern internet lifestyle.
Some say 5 minutes ever, with option to pause game up to 24 hours.

2) Strict league entrance.
Currently it says like 5 finished games in last month.
May be there should be option at league creation. Like, only accept those who done 1000 moves done last month. (That's average player, based on most active doing 3000)