Let me see if I've got this straight...
The difference between you and McBans is that you're mod based as opposed to plugin based, you can only recieve global bans from servers you trust with this "Opt-in" system. You also store chat, command and chunk logs to your server where "It will be available for the public to see."
Okay, this is what you have basically. It's Batman's Sonar Device from the Dark Knight with a user consent requirement. Say that servers take your mod and install it, not only is it erasing all privacy from people whether they like it or not -- And don't correct me by saying they have a choice, because they don't and I'll tell you why in a sec -- But it's also leaving them open to bans that they quite frankly don't deserve. It's simple to say they've been given the benefit of the doubt but I really don't think, and I wager you don't think it'll last very long once the spectacular number of ban appeals comes in and you're forced to make decisions you REALLY don't want to make.
As for their "choice" in the matter. Assuming I'm correct in saying you only enter this agreement by opting into the mod on your server, then server owners will make it their BUSINESS to make others opt in before they can play. Think I'm over exaggerating? You need to play more servers. It isn't a democracy to them. It's a dictatorship. But then you could argue that you could allow members to willingly opt in to the mod itself without the server middle man so that there's no forced hand. But oh wait -- There is. Assuming the mod itself won't have the option of autokicking those who aren't opted into the mod, they will do it themselves so that they have full control of their players.
I was never comfortable with the McBans system. I'm even less comfortable with this.
