It looks like an interesting addition. I'm curious to see if they make any changes regarding determination of when you are in and out of combat, with regards to ECM/ECCM.
The way it currently works, once contact is made, initiative is set. So the side with the higher initiative tends to move first. This can result in what appears to be a double (or free move) for one side (usually the PC side).
I don't see it impacting high difficulty mission tactics a lot, unless you can add ECCM/ECM devices to any mech. If they are restricted to specialized mechs (which are not Assault class) they won't get used in high difficulty missions (5 skull) where the player is always outnumbered by at least 2-1 and often 3-1.