For me, taking a risk at a small scar is a small price to pay to get a snake eatting again. If ever I thought my snake would be in danger from a live mouse, I wouldn't leave it unattended. I left the mouse some cardboard to shred on his own. I was more worried about the mouse chewing through the tub enough to escape.
While is may seem cruel to risk bodily harm for a greater good, I for one am all for it.
A few scars or a bloody dying snake?
No offense, but there are better ways to go about it and risking your snake's life is not one of them.