For anyone who is wondering how to restrict the visibility of the addaction selection to just one person:
Create a condition on the addaction for distance and make it something the game engine wont allow your character to reach in relation to the person "with the bomb". I managed that with this:
arm = terrorist1 addaction [("<t color=""#FC2B05"">Arm Bomb</t>"),"suicidebomb\armbomb.sqf",nil,1,false,true,"","((_target distance _this) <0.2)"];
With this, just the player, in this case "terrorist1", is able to use the action created because the others cant get close enough to the character to activate the script. This also hides the appearing red text from other players unless they reach 20cm from his body, allowing the suicide bomber more security in a pvp scenario.
I have not tested this on a dedicated host yet and could not tell you if it creates problems, but it seems to work on a local host and editor.