Unfortunately, this is not a function currently possible and it might require too much drastic change to the way the web-ui is designed to get it implemented in the current version.
It would be possible to create read-only users, but in doing so, I would be forced to move away from Linux-users, and instead have non-system, web-ui-only usernames, which could make for managerial headaches, but also a lot more granular control. Hopefully we’ll see a discussion bloom.
For the upcoming iteration, vote for this functionality in this poll.