1. i have seen the nuke beacons by the control panel in the weapons shop and there is nothing wrong with putting them there - its perfectly disarmable and anyone in the place where the vehicles come out can see it clear as day (its just the fact no one really goes in there )

2. setting them on top of the infintry barracks in the field map (i think) - places where you can get that arent a glitch (ie - someone standing halfway into your computer screen would be a glitch (thus you cant stand on the wall terminals)) should be fine to set them in