Most of the hard work is already done for this: Puppet, Chef, etc.
If I were going to build this, I'd take a look at Blueprint, since it (at least in theory) can reverse engineer what's installed on a running server.
I would be curious if there was an open source tool that copies your current security groups and writes them to other regions.
Hint, hint…
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† I too did an us-east-1 to us-west-2 move on Monday, and it was unfun.
I'd love to hear of an s3 based approach.
https://cloudyscripts.com/tool/show/5
You can also use the APIs to do that S3 copy I mentioned. Here are one of the many write ups of that technique.