[Mobhack]

Its as simple as this - whoever you have currently selected on entering the bombardment is the controller for any new adjustments made in the bombardment screen.

There is NO requirement that if battery Z is initially called in by Observer O that you need to only ever use O as its dedicated personal controller. If observer (or command unit) P has LOS to the impact and is the current unit selected in the bombardment screen, it can happily adjust battery Z's mission.

So multiple observers are only needed in order to have several different LOS arcs. Or to give you a few more gold spots, but if the observer is skilled or is 1990s level tech then they can call in fires on impromptu targets fairly quickly anyway, and most gold spots plotted seem to be wasted as the battle occurs elsewhere, in my experience. Gold spots are useful in the early period or in WW2 - or if you have an inexperienced FO. In campaign games, the FO is very valuable (esp in WW2!) so that you do not want to put him where enemy arty will fire.

You could simply use A0, but he isn't as skilled as a dedicated FO at least till he has gained a lot of experience - and as he wont be racking up kills, he will only pick up slowly over time.

I find one FO does the job, and I mainly fire and adjust "blind" without having any need to bother with carting him round the battlefield in a jeep to gain LOS arcs onto targets. In MBT, a foot FO with TI or a radar on a hilltop in my rear zone is all I bother with. If he has LOS to the target, then it's gravy but I do not obsess about manoeuvring him about the place, I do obsess about placing him somewhere the enemy is not likely to drop a shed-load of arty onto because something attracted its attention like say nearby MRL blasting away for a couple of turns, though. I want him well away from anybody else, and preferably on a nice big hill with a good vista.