It's an interesting idea, but I'm not sure it works.

My main objection is the real nature/purpose of the Binder. It was a ter'angreal meant to defeat AS criminals refusing to amend their ways, and it seems obvious it was designed to be as safe as possible.

It doesn't make much sense to put a reverse/failsafe button on a tool that was used to sentence AS criminals. The way to stop the procedure is already to stop channelling spirit into it, and the way to reverse the procedure is to activate the Binder and revoke the oaths. There's no obvious need for anything more, and it would just jeopardize the safety of a tool you don't want to have any loophole/failing.

Given the Binder was trusted to bind extremely dangerous people (like Semirhage, who managed to avoid this by escaping), my guess would be that there are no widely known way to defeat the OR during the procedure (or it's something terribly obvious and easily taken care of). It's also highly probable that you need to use the same OR to free yourself of the binding (otherwise this leave the door open for a criminal to find a black market binder). It sounds likely each Binder creates a unique weave, and to reverse the procedure you must use the same Binder. It seems that the weave (akin to a net of compulsion would be my guess, a kind of auto compulsion) the Binder makes is inverted, perhaps for safety and making it virtually impossible to unravel (without killing the person who's bound, anyway). All this would just increase Mesaana's will not to get herself bound at any cost. Let's remember the major downside (the risk of losing half of her remaining lifespan, or dying right away aside.. but perhaps the DO's immortality takes care of this) was that she would lose the capacity to use the OP as a weapon (expect against Shadowspawn and DF, ironically) before she was under attack. She would be stuck with conditionning herself that her life is in danger at all time.

The only possibility I see is that the AS don't respect the proper procedure to bind someone. The procedure may perhaps be interferred with with channelling (warding/shielding your brain against the Binder's weaves, for instance), and thus the proper way to bind someone involved shielding the person first, or warding the Binder so any channelling other than the spirit thread is automatically detected. The AS don't do this, so they leave open a door to someone using inverted weaves during the procedure (by the criminal or an ally in the room).

But I'm doubtful of all these solutions. The only thing "obvious" is that we know the Binder was meant for use on criminal, and that the AS are "playing" with something they don't really understand, and have created loopholes in the oaths. We might surmise other loopholes exist because they don't respect the proper procedure to bind someone either (though Sammael gave no such warning to Sevanna)

Brandon seemed to speak of many ways in which the Binder can be defeated, and seemed to imply the way Mesaana used can be puzzled out from what we know. That's really not obvious, unless by "defeating the OR" he meant defeating the test on the OR Egwene imposed to all sisters. There are quite a few obvious solutions then, if he meant Mesaana has defeated the test somehow. Let's say Mesaana was Danelle. She just had to abandon that disguise the night the BA fled, and take that of someone inconspicuous (servants, novices etc.). After the testing, she could adopt the identity of a sister who has passed the test (kidnapping/killing her first, of course). Mesaana has been in the Tower for a long time, and by now must known other solitary sisters than just the one she replaced (if Graendal was right, anyway). Even more simple would be to have taken as her new disguise someone who won't have to swear the oaths at all. It sounds very unlikely Mesaana needs a high profile disguise anymore, because without the BA in the Tower, she'd need a really really high profile one (even a Sitter wouldn't be enough) to accomplish anything politically oriented). As for spying, without the BA to help, she's quite screwed(unless she's created herself this army of agents among the novices, anyway - and even then, sisters who discuss important matters when novices are in attendance often ward their conversations). It's not obvious what she hopes to do by remaining in the Tower, especially if she has no DF network among the servants or the novices. A novice might actually work better now than a random low-profile sister. AS aren't suspicious of novices, but as long as Mesaana is not captured/killed, Egwene will be suspicious of all sisters. It all depends on how long Mesaana intends to stay, and what she is seeking to accomplish. That determines the sort of alias that best suits her... the one(s) she used to have, a new one and from which group of people in TV. If her target is Egwene herself, she's pretty much limited to her inner circle (Siuan, Leanne, Silviana or someone "random" like a novice attending her on the right day etc. and of course there's Chesa. Chesa's probably the most dangerous woman Mesaana could choose to replace, but she could only pull it off for a one shot deal. She can't interact with Egwene much, or Egwene will puzzle out it's not Chesa almost right away. It's a very dangerous disguise to enter Egwene's rooms in the night, and strike at her the next morning, when "Chesa" enters to help her wash and dress up), and this implies this wouldn't be the disguise she uses yet, she'll only take this MoM in the scene where she attacks Egwene.

If her intent is to learn as much as possible about Egwene's intents, then she's better start compelling a lot of people soon.. Sitters, Silviana etc.

Of course, Egwene was a little too open about Verin and her hunt. She wanted to clear Verin's name, but she should really have waited longer for that. Mesaana or Alviarin obviously had spies among the rebels who aren't sisters/BA: DF servants/secretaries, novices etc. Mesaana's been involved with Verin, . By revealing to sisters Verin was the one who betrayed the Shadow (the story will then spread like wildfire among all sisters, and where non-AS will hear), Egwene most likely put Mesaana on her guard, and might have started the very chain of events that ended with Mesaana remaining in the Tower. Perhaps SH forced Mesaana to stay and find out what else Verin has betrayed. Perhaps Mesaana isn't allowed to leave until she finds that out, and this means she would have to get close to Egwene.