I don't mind them eating whole prey. It's natural for them and has everything they need (organ meat, muscle meat, bones, connective tissues, ect) all in one neat and tidy package. There is very little blood but on occasion the ferret doesn't like to eat the whole thing and wants to save some for later. Twitch is known to eat the head and top torso but leave the bottom half for later. You can feed them frozen/thawed no problem. Ours get f/t all the time, especially when I'm out of live (which is often). They won't be so keen to eat a frozen feeder animal, but you could always try. No harm in trying. In the wild, they will bury their leftovers in the winter so those would freeze and they would come back and eat the frozen meat so it wouldn't hurt to try. (I'll give it a go and let you know)
And you don't have to feed whole prey at all. You can stick to raw meat, meaty bones, and organ meats. Many people do this, but its all about variety. Mine get several different types of meat along with chicken legs, turkey necks, and chicken wings. <- They love bones. (Just don't cook them).
We just got our fourth little ferret tonight. So now we have two girls and two boys.We are so excited. And it looks like the gerbil should be popping soon.