we need a check mechanic to avoid teleporting/placing items/units where a player can see it

the simples method is for this a line of sight(LOS) check.
if the Game Master(GM) interact with an object and a player haves a LOS to the source/destination of the object the color of the marker changes. if he tryes to place if he gets a accustic warning.
but he can force the placement if he repeates the command (i.e dubble click for placement).

this avoids accidents