This probably isn't feasible with the current Demonbuddy but I don't think it's necessarily impossible if someone devotes a little bit of time to it.
Basically this profile would monitor the number of Keys in your stash and pick an act to run based on that information. If I were to end up with six Keys from A1, four from A2, and none from A3, the profile would run A3 until I had four, then alternate between A2 and A3 (since they're tied), always focusing on the act with the least amount of keys. I know it has to bother a couple people when they wake up and have nine keys in their inventory all from the same act, and they have to run some specific profiles before being able to run Ubers!
Basically this profile would monitor the number of Keys in your stash and pick an act to run based on that information. If I were to end up with six Keys from A1, four from A2, and none from A3, the profile would run A3 until I had four, then alternate between A2 and A3 (since they're tied), always focusing on the act with the least amount of keys. I know it has to bother a couple people when they wake up and have nine keys in their inventory all from the same act, and they have to run some specific profiles before being able to run Ubers!