This feature is very cool, but it would be nice if it was actually possible to cut the npc off from escaping. I mean, forcing him to go for the grids would be a perfect solution, otherwise it feels really cheap and a little bit inconsistent for the npc to leave the map via a route that isn't available to players. Right now you just have to metal gear solid those missions and you're mostly screwed is you trigger the alarm, which makes them somewhat annoying to farm and very easy to fail, at least when compared with the other assignment types.
I don't want to see NPC escapes removed from the game as they spice things up, juat give us some viable counterplay aside from luring the guards towards the grid to kill them away from the others all the time.