Buttons visible to allies but not the owner

[MichaelWilson]

okay so, suppose:

Player 1 builds barracks

player 1 sees the standard buttons for a barracks

player 2 ally of player 1 selects player 1's barracks and sees

buy footman buy rifleman etc etc
the units have stock and stock intervals
are trained instantly like and merc camp

but from p1's perspective its the normal train units buttons
and they enter production que , are unlimited etc etc
does this need triggers or is there a way to do this with just custom abilities?
if it does need triggers could someone either walk me through the steps (i have zero experience with triggers or jass/vjass)[i would prefer being walked through so i can learn] or writ it for me?

 

[Daffa]

Full Shared Unit Control.

Is this map specific? Is the allegiances predetermined in the map (fixed player setting = on?)?

 

[Pyrogasm]

Full Shared Unit Control.

That would just mean player 2 can train units in the production queue too, but wouldn't make them train instantly like sold units.