OnlyOffice editors and Owncloud is a match made in heaven. But the match should live inside owncloud not the other way around (they have webdav backend support) which seems to be the only available option at the moment.
They have fully integratable online editors that are better than Zoho Google or Microsoft.
I am really surprised this hasnt been picked up by someone already.
This can certainly be done by OnlyOffice if they have an interest to do this and they can offer it to the ownCloud Community. We are currently working with Collabora Productivity on Collabora Online and have just announced Version 2.0. Did you check it out yet? This is following a mandate from security challenged customers that they like to have full access to source code and full modification rights to their ownCloud system running in the enterprise or at their end users devices.
On behalf of all the developers of ONLYOFFICE I'm going to tell now that we are already working on this plugin 
Perfect. Please email me at hd (at) owncloud (dot) com. And don't hesitate to reach out for any development assistance you might need. We are also working on a marketplace!
plz let me know if you need a super motivated beta tester! vedat (at) nommaz (dot) com. otherwise i will be monitoring https://apps.owncloud.com/ daily to get it as soon as it is out!!
any news on the progress auf this addon?
I'm also interested to know.
its out and works really well!
The link to the app:
https://apps.owncloud.com/content/show.php/ONLYOFFICE?content=174798
Thanks a lot for sharing the link:)
I tried using the app and directing it to the ip of my Only office server but when I try to open a document from within own cloud it tells me that the app needs to be configured.
I cannot install this app from Apps repository - after I click "Enable" I receive "Archive does not contain a directory named onlyoffice" information... Any fix for this?
Please report such issues directly to the app developer(s). The issue tracker for this app is available here:
Contact the developer directly I would say.