Is it possible to use update.zip as rescue?

[eggsped]

The wife has a new D2, soon to be rooted, and she is getting an update notification. Can I root the phone, save a copy of the update.zip to my pc, unroot, let update proceed, reroot and use the copy of the update.zip file as a way to recover the phone should I get stuck in a bootloop?

I have sbf's but I'm thinking this may be an easy way to recover should I hit a wall with the phone. I had a D2, exchanged for X, and had to SBF a couple of times in the <3weeks I had the phone. When I was stuck in a bootloop it seemed like Clockwork was gone because I would get the stock recovery.