[...] players must declare which troop possessing the Forward Observer Special Skill from their Army List is their Liaison Officer. The trooper chosen must be always one of the models or Markers deployed on the game table. Players are not allowed to choose troopers in Hidden Deployment. Also, troops whose Troop Type is REM are not eligible to be Liaison Officers. At the end of the game, [...] make a WIP+3 Roll using the Liaison Officer’s WIP. If the roll is successful, the player will get 1 extra Objective Point (up to a maximum of 10 Objective Points). So you can choose markers and it has to be a Forward Observer. Do you choose the Ninja, skip Hidden Deployment and try to keep it alive? Do you invest in a Karakuri, even if it does not fit in your game plan? Do you choose the Keisotsu and pray nobody remembers that rule? Or do you completely ignore this extra?
I already use Forward Observers a lot, as they have some nicely useful extra utility beyond just being a specialist, so if there's a Keisotsu FO already in a given list, it'll probably be that guy, though I'd probably take him out of a core link, if that's where they were, and leave them prone on top of a building somewhere, cowering in fear, and hoping my opponent forgets about them. Preferably the tallest building I can reach during deployment. If there's a Karakuri already in the list, they seem the obvious choice, given how survivable they are, but I think, for me anyway, I'm not going to expressly try to shoehorn something extra into a list to maybe get an extra OP with, if it survives.
Karakuri for acquisition and frontline to also get that 1 extra point for controlling tech-coffin/central sector. If I go first she have most chances to survive last turn of opponent. And I will move her in midfield anyway. If it's haris, then heavy shotgun one to be able to safely advance with mk12. If I somehow can't afford karakuri then it would be keisotsu. Ninja costs almost same as karakuri and loses HD, also squishy. Probably domaru also not bad option if you field samurai fireteam of any kind, but I personally do not play them for the moment. For safe area it always would be keisotsu, even if I have karakuris. I can always move him 1"+ in last turn from whatever total cover/roof I've found in my DZ. And if my opponent tryes to kill him instead of doing whatever else, than the game most probably had came to a point when it's already lost. On the second thought ninja could be good for frontline and safe area if you can find hard to access spot in home quadrant/central area and deploy it there. And it's 35pts already scoring and giving you up to 2 extra OP.