I don't feed live anymore for a number of reasons but I'm not going to try and change your mind. It's your choice. I used to do it simply because back then I didn't know f/t even existed and at the time I wasn't comfortable with killing the rat myself for pre-killed. I think removing the animal from their enclosure is a lot more disruptive than removing some items, but I still think removing the items is probably pretty disruptive, especially if you say you are trying to give "enrichment" through the hunting process. I understand wanting to be able to observe and make sure the rat isn't attacking him, so I think the solution might be to change what you have in the enclosure so it's still cluttered and feels like it has "hiding spots" to her, but you can still see what's going on. This is not really an option if you want things looking really naturalistic, but you could use translucent plastic hides that give them the cozy feeling of a burrow and block some light, but you can still view, and then whatever else like plants and things are in there aren't so cluttered that you have huge blind spots.

If you change your mind about live feeding, here is my method to thawing that makes things really easy (I have a lot of snakes to feed, especially when I've got a bunch of hatchlings, and I don't have time to waste):
-One or two days before feeding depending on the size of rodent I take the prey items I will be feeding out of the freezer and put them in the fridge, so I don't have to mess around swapping water over and over to keep it thawing safely.
-About 15-20 mins before feeding I put the prey (still in a ziplock) in a large pot of hot water and set myself a timer on my phone and go do something else while I wait.
-Timer goes off, I feed the snake, and unless it's a hatchling or snake I'm trying to switch to a different food, I just offer the item and it's usually struck immediately. If not, I set it on a hide and close the enclosure up and go about whatever I need to do and check back an hour later or so and grab it out to throw away if it didn't get eaten.
To me this process is a heck of a lot easier than dealing with live rodents, which I still do from time to time for stubborn hatchlings.