Why it is for balance? If someone is freekilled, the warden can slay them. So, I see no point in this rule protecting the reds because warden can slay the blue who freekilled. Demo's sticky are banned because they can cause mass-freekill unlike the heavy's mini-gun and sniper's rifle. About the tunnel vision, when I go sniper I observe the area the reds are in which is helpful for the warden and encourages the reds not to rebel. The heavy revving the mini-gun can be annoying but you could say the same thing with AFK taunt that make noise and voice commands.
It's not for balance because of the potential for mass freekill; rather, it's to balance out Heavy's and Sniper's potential damage output vs melee only REDs. The tunnel vision is just an added bonus to the rule, not the main component. And yes taunts and voice commands are annoying, but the warden can deal with that.
Eh. For the sniper, it's ridiculously unfair that they have to take double as long to kill someone compared to all other classes since they have to scope in, aim all over again and then shoot rather than a scout who just has to press mouse1... Even harder for inexperienced snipers. This discourages guards from going sniper, which is a necessary class for jailbreak in, as you said, the grand scheme of things.
Guards should be encouraged to play multiple different classes to fill niches in the guard team. Not only is Sniper probably the best class overall for the Guard team now, letting them scope in all the time will just create a wall of Snipers. Not very fun IMO.
"As a heavy you do much more damage when your minigun is spun up" Does that relate to baiting at all? So we are nerf classes because they can do more damage. What about sniper? Just because he is one of the most overpowered classes in the game, doesn't mean we have to nerf him for no reason. We could say that the spy is overpowered as well because he can one hit kill. We could say medics rebelling on red with Uber are overpowered so why don't we nerf them?
Also, that is not a real reason why baiting is a slayable offence. The blue is not allowed to kill the red so what is the point of punishing a blue for baiting. So what if the reds cannot chase baiter, baiter are just baiting and not affecting the flow of the game. You can just ignore baiting. Please tell me another reason why baiting is slayable. So, can the warden be slayed for baiting because warden can bait.
Let me ask you this: as a Warden, is it not frustrating and counterproductive to see BLUs put themselves in harm's way other than being dumb? We slay BLUs for baiting because it is not helpful to the warden. Continuous baiting will result in a teamban, thereby creating a spot on BLU for a more helpful guard. Again, (and perhaps its confusing and should be better clarified) think of Heavy's revving and Sniper's scoping as a balance for Jailbreak, not as actual baiting. Heavys and Snipers with the ability to react that fast have been determined to be a little unbalanced and unfair for REDs. Not to mention the other benefits. Like I said, if there was enough support to remove those restrictions, (I suggest starting with Sniper, I think it's a better argument) then I could see it changing.