A few things that come to mind:
- Most important: retain the authority of the incoming backlinks. So ideally, you’ll keep the existing URLs so that any incoming backlinks remain valid. Alternatively, you could set 301 (permanent!) redirects to the corresponding new URLs but I think this can take away some “link juice”.
- You’ll have to implement URLs / routes for the BAP Client yourself because it doesn’t come out of the box. See also this related thread: Implementing a Router for bap-client - #2 by akehr
- You’ll also need a custom solution to allow access to the form engine without login. Perhaps the concept of “anonymous access” in A12 can come in handy.
- Make sure your new site runs either canonically on www or non-www but not both. That would make every page duplicate content.