How to migrate CWP - CWP 2nd time for existing site?

I am setting up a new CWP server. Haven't made it the live server yet.
As part of my config/testing, I copied over all my websites. They all work great, 100%! Including SSL certificates.

HERE'S MY PROBLEM:
I did the test weeks ago. I need to do "the big switchover" which includes copying over the latest databases, files, etc.
For some simple sites I can just upload the changed files by FTP. But 2 of my sites are quite complex. I'd like to use CWP - CWP migrate feature, but I can't do that without deleting the sites first! And that would mean undoing the (manual) work I did to get SSL working.

Is there some way to "restore a backup" from another server, or something? Basically use a PART of the CWP-CWP migrate script/process? Because right now, there's a green checkbox and I can't check "Just update files please" or anything like that.

It seems to be a very useful, necessary feature.

how if we made it more simple
use backup beta
download the compress file
put the file in same folder--subfolder like at first cwp
then at second cwp just go to backup beta
restore