No worries at all Fluury! This would be a nice addition if I can pull it off xD I'm not sure how it will act if your holding down the left click when it switches brushes but I can def look in to this :)
I'd be intrested to see the brushes that you are using to toggle between, I'm asuming they would be more like paterns then objects in that case. Maybe even with varying opacities?
I def could see this being powerful with a random rotation interval too. Would be like many custom brushes you find in other programs xD My only worry would be to see how quickly it could adjust the brush on the fly but I can put it to the test to try and push it to the limit like I did with the swaping xD I was pretty surprised how quick it was swaping between brushes.
Here is a little video I posted when testing the swapping just in case quickly swapping needed to be done
But yeah could be neato to add a feature such as this. I've not played with having a function fired off at a set time interval nor do I know if it's possible but I can take a look!