Baby's not due for a couple months so this is all theoretical.
I understand that the reason for boiling the water is to sterilise the powder so you do need to mix the powder with hot boiled water, I also understand it's best to make the bottle up as you need them put I imagine you're making them up for a hungry baby who probably doesn't want to wait half an hour for the water to cool.
Can you mix the powder with hot boiled water (slightly cooled
But hot enough to sterilise the powder) and then mix in cold pre boiled water to help cool quicker, so adding two different lots of water totalling the same amount?