Having never really played ARMA I cant really comment on the previous implementations of BattlEye, but I do know that ARMA's game engine was very much script reliant, so they needed something on the client side to stop malicious scripts/coding from hiding in amongst it. I'm just not sure that we need such a heavy tool for Ark, it almost seems to be using a cannon to kill a mosquito?!
We have NOT implemented it on our server, as if you can trust you mates who can you trust?!
As for the Linux/Mac issues according to one of the devs they haven't signed the contract of BattlEye yet but they are giving them "no small amount of money to do something [fix the Mac/Linux issue] they were already working on.. only faster"
but I do think they should have waited until this had been resolved before rolling it out to servers, locking these users out until the issue had been resolved!