Need Some Ideas : Good Method For Multiple Players To Switch Between Heroes

I'm creating a map that has a number of AI-controlled heroes in it. At any time, a player can select a unit and take control over it. If a player is controlling a hero, he can either switch control to a different hero or relinquish control and watch the AI continue to fight.

I'm trying to devise a way for the players to switch easily between heroes.

My current solution is to have one "take control" hero button and one "relinquish control" hero button--using dummy hero units to place their portraits in the left-hand side of the screen and detecting when they're selected to perform the related task; however, then--when all heroes are under AI control--you only get to see 4 of the 6 available.

Does anyone have any ideas that would be equally user-friendly without consuming a hero space?

There are no ability spaces available on the units.

Have a building in corner of map with ability control unit.

A player can hotkey the building for simple use. He then just needs to use the buildings ability to gain control of a unit.

Thats one way
Depending on how many heroes there are, you could give the building an ability for each specific hero, allowing players to just click a hotket to automatically take over a hero they want.

Assuming you dont want clashes been control, you could add/remove the abilities from the buildings as heroes become available/unavailable.

Just remember the simplest way iis often the best :-)

Well if you wanted it to be REALLY easy you could have a trigger so that if a player selects a unit and that unit is on the AI team it automatically gives control to the player. Then if they select some other unit it goes back to the AI team.