Of course it is possible to go with an invisible "collision sprite" which is attached to the Bot object. But in my final application I will have a lot of objects on the scene at the same time and then it will be crucial for the performance to not having to use 2 sprites for each Bot object. As that will slow down performance.
But I'll have like 100 instances of the Bot class. And then there will be a quite big change to add 100 sprites more as I'm sure you understand. That will effect the performance more than a couple of events.
Though I'm not sure if it's possible to do this with just events. So I might have to go with the collision sprite solution anyway.