ArmA 3 is missing a replay recording feature. In order to capture action your only choice is to use a CPU/Memeory and HDD resource draining third party program that also gives the user the ability to record only his POV.
What the game needs is a replay recording function similar to HLTV or GOTV that records the coordinates and actions players and the abiltiy to reproduce them, like all the other modern games.
Since this is available in VBS2 it is possible to introduce it in the game, without much effort.
Clearly it is one of the most useful tools that modern games have for many reasons.