Boardstate-related effect durations should start when getting added to stack

This might be tricky:

> If Rubinia Soulsinger stops being tapped before its ability resolves — even if it becomes tapped again right away — you won’t gain control of the targeted creature at all. The same is true if you lose control of Rubinia Soulsinger before the ability resolves.

It matters for when you untap her after the first activation: you shouldn't be able to gain control of more than one creature like that.