As another daily Freeplane user, anything not self-hosted and behind a firewall is a no-go for me. Sensitive or not, having someone over your shoulder kills the creative juices. None of the things you mentioned except for split view sounds like an improvement over Freeplane which is an open-source serverless app and great for the power-user.
Perhaps a useful feature for someone like me would be the an online app where I could import a mind map from another program and then choose from a variety of presentation options, and be provided code for an interactive embedded mind map in a blog or website. That would be enticing to people who aren't ready to dump all the features they are used to, and that crowd is much more likely to jump on to something like this than the average person.