First of all, live blackjacks are played with 8 decks and there is cutting card put in the middle and more likely you only play with 4 deck. Once shoe is unready, this 4 deck is shuffled with another 4 deck that wasn't used in game. There is possibility that shuffle quality won't be high and it may end up like it may be possible for players to count cards but in this case scanner counts all cards and shows the shuffle quality of each shoe. If it's lower than, for example 80-90% or something like this, then whole game is cancelled and letter goes to casino department / players from live blackjack supplier. Also, not only that, every player is monitored and if it seems like someone wins and wins a lot, then a lot of things are checked by risk analyst that includes shuffle quality, dealer's live performance and so on.
Also want to add that once a day, all cards are changed on all table for further security and for overall game performance (old cards are bad in this case).
You can do whatever security you want, but if the player wants to cheat, he will try to cheat, it will be casinos job to catch the way you explained, but its their responsibility so the ball is on their court, if the casino misses, the player will basically cheat the system, if the casino catches, then player is caught and can't do it anymore.
I am not saying the system doesn't work, I am just saying that its a risk, you have to be on your toes as casino and if you are not careful and if you do not do your due diligence with the player well, you may get some cheater out of your hands and he could withdraw until you figure it out. Hence what I am saying is, obviously most cheaters will be caught, but 100% catch rate is a very difficult thing to handle.
Seems you didn't understand at all meaning of my post. Player can't cheat in live casino, that's impossible if we don't mean bugs but in any way, that attempt is meaningless. The only risk that's involved here besides what's alredy mentioned, is that dealer/shuffler may know player and will try to make him/her win. This can be done by seeing hidden card and then telling player by mimics or etc whether they'll win or not.
There was even one accident in Riga when shuffler had camera on his shirt and it was like he could record video from and was shuffling in a way where it was possible for camera to catch the cards and make player understand what cards they were, as a result, player won a lot. But as I told you, there is constant monitoring of everything, everywhere and this was fixed pretty soon. There are floor supervisors for that, shuffler team leaders, risk analysts, customer supports, service managers, schedulers and etc that monitor all of these.
Risks to cheat from employees are minimal and in case, fixed very quickly. On another hand, player can't cheat on his own.