There is a story about google's ID verification I read just this morning that would be relevant to your question. It seams that if people report your name as fake or for impersonation, a simple photo ID scanned and emailed is all you need to get back on course. As it turns out in the story, even a fake photo ID will pass the test and get your account a green light.
This is not currently possible. I have browsed the list of Chrome extensions and userscripts and there isn't anything that accomplishes your task. Best to wait for the API to reach read state.
Also popular social networks do not handle their import this way. Mass subscription sounds like something Google would try to prevent in the same way Twitter prevents that service.
Best Answer
Make sure you're logged in to your Google Account. Go to your profile in "Classic" G+.
"View profile as yourself".
Click the "About" tab.
Scroll down until you see the "Basic Information" block.
Click "Edit".