> "The site boundaries will be a problem as they will have to overlap"
First, don't confuse site assignment and service location boundary groups. Only boundaries specified within site assignment boundary groups cannot overlap.
Next, you don't actually need any boundaries specified for site assignment (aka within site assignment boundary groups) for normal ConfigMgr operations. The only thing that won't work without these is auto client push.
CB is close enough in most aspects to 2012 that there isn't a huge learning curve involved or training necessary. Not deploying CB now and instead deploying a 6 year old product would be a mistake.
Jason | https://home.configmgrftw.com | @jasonsandys