It is much safer to feed frozen, live rodents are as likely to do harm to your snake as the snake is to the rodent. It can be very difficult to switch a BP to frozen so why mess that up?
Frozen rodents are not frozen alive, they are euthionized in a humane way.
You should feed the same size rodents frozen or live.
Is there a reason why you want to switch?
There is no reason to be afraid of reaching into the tank, this is part of owning a BP... What if the live rodent bites your snake? You will have to reach in and stop the rodent.