I created a bot like this. https://github.com/daniel-lxs/BotIt
It's intended for links and I wouldn't encourage using it for anything else, as you said I think the best idea is to crosspost content that isn't on reddit on the first place, and just use reddit as a way to measure how engaging is the post.
This is so far a work in progress so expect bugs. But in my opinion, the bot is usable in this stage.

Edit: I might add multiple subreddit and magazine/community support, so you could specify a map and pull from many places to post in many places, stay tuned.