Dota Hero Select unit

Can anyone tell me this thing about the dota hero select unit(The circle of power is the unit used to pick hero in dota)How can i make it so the unit is not able to be used to choose hero but is able to be used to revive heros in tavern?

my guess is just make it a building with the model of a circle of power or just use the doodad... buildings cant buy things units can then just do a trigger to add the hero icon to the thing as a revive.. i dunno any easier way