We had some chat with the developers of https://rocket.chat/ - rocket.chat is also taking part in GSoC 2017.
We agreed on running an integration of rocket.chat within owncloud under our GSoC mentorship with help of rocket.chat mentors!
The basic idea is that the rocket chat front end is integrated within owncloud as an app - either by iframing or by loading the necessary frontend javascript elements within the owncloud front end.
We need to see how we can then provide some further integration like pasting link shares, upload files from owncloud into rocket chat, invite owncloud users to join rocket.chat .....