I agree that’s a needed option. Guess we will have to wait until G+ opens an API for WordPress to connect to.
In the meantime you can set up a free account at https://www.hootsuite.com and add your G+ account. Then use their publisher feature to grab your feed and publish it on G+. Works fine for me, with the exception that posts without a default featured image will not have a thumbnail, and a gravatar only works through publisher.
Your feed is at your blog address /feed/ or if you only want to feed a certain category, that works too, just add /feed/ after a category.
https://www.fidosysop.org/category/syndication/news-syndication/feed/
Best wishes.