I suggest more that BMVs are able to bypass the two discorver rolls if you succeed on the first one. In addition to what they already do. This would make assassination hard if a BMV is nearby, even more if it is a Bao MSV2.
While I'm generally leery of auto-anything in this game, I might be OK with that. Or maybe outright forcing any Impersonator to deploy in IMP2, with a bonus to discover. "What's Bob from accounting doing here? ... ... Wait, that's NOT BOB!!!"
With Tohaa I can get a 12-point trooper with Biometric Visor Lv2. CA or Haqq players wouldn't like that ruling change.
"Kazak/Keisotsu/Zhanshi/etc Ahmed, here from HQ to provide support" is typically what I use, mostly because we have a guy called Ahmed who it amuses us to insinuate is inherently treacherous after years of brutal RPG experiences...
But it would fit into the fluff. And atm there is no direct counter to Impersonators. Same faction have possibilities if the deploy second but that binds roughly the same ammount of points of the cost of them.
But the question is: is the game in balance atm with impersonation? I don't know it, but every game effect should be able to be countered, what isn't the case with impersonation, what will usually cost you uncounterable 1-X models.
There's no direct counter to anything in the game. Biometric Visors can be a good way to deal with these things though. If you're on the active and hunting an impersonation marker down, for example. Going first and having to deal with that lurking marker is tricky.
No they cannot. If I know my enemy has a big TAG or Lt (or Lt TAG) I can make a single, unstoppable attempt at killing it regardless of how many Biometric Visors, and their levels (the L2 is quite... meh) in a suicide charge with a Speculo Killer. Remember Shasvastii get 2, and I heard rumors of those being Minelayer for free aswell. Maybe being able to "cut" the charge with the Biometric Lv2 would make things balanced again, but as it is now the Biometric does not really change the high risk/extreme reward of an Impersonator's suicide charge against the enemy Lt/TAG.
And yet you will, anyway. Bow down to the will of Lord Bostria! And eat a good sandwitch in the meantime :D
Speculo is not unbalanced. Chance to take down any model is not so high. First you must pass wip roll, win close combat after, and enemy have to pass dam.12 save finally, if you are successfull at previous two. Rounded up it is way less than 50% chance to kill enemy model in suicide attack with speculo.
Defending against Impersonation has always been about stopping the second kill. Because just like attacking out of camo, you have a decent % of getting the first kill. Or so I thought, until I actually did the stupid math. See below. OK, Shas LTs are all WIP13. That's about average, which makes it a 50% chance to go first. Then it's a 65% to deploy inside the enemy's DZ (may not be necessary, but for worst-case odds we will assume it is). Again going for the worst possible opponent to attempt to kill, an O-Yoroi TAG (Highest CC model with highest points cost. Unless someone has a better idea!), which is a 49% chance of winning CC and killing the TAG with the MonoCCW. .5*.65*.49= 15.925% chance of everything going right and killing the TAG.
Achilles. Worst target is also relative. O-Yoroi will nearly guaranteed have a CoC backing them up and is not all too likely to be the LT. Getting your opponent into LoL is so much more valuable than taking down a TAG. You don't necessarily need to infiltrate into the opponent's DZ if you go first. Since Impersonation has two layers, it's very, very, doable to simply Move to where you need to go - regardless of number of BioVs - and you don't really care about mines, now do you? What minelayer does is that it makes it so much harder to dig a Speculo out if you deploy it defensively making it eat even more orders and it also means there would be a very good incentive to do the infiltration roll if you go second or when you're up against a strong fireteam. Going second against Varuna? Infiltrate a speculo or two, placing the mine(s) so that it overlaps the soft parts of the Kamau fireteam and no more problems from them!
That's not a fair assumption. You will take this option in <20% of the cases. Therefore you have a 25% chance for success. Not great, but also not awful for the possible result. And if I'm correct, the best use of them is not to kill the main pieces but the chearleader.