owncloud now is nextcloud(nextcloud.com) and all features is open source,when you add this feature you will help alot because you have implement dropbox and gdrive,but is not encrypted and it should be.
by having nextcloud implementation you solve alot of problems like :
1)instead of adding all external drivers providers witch can take alot of time,you just implement nextcloud,and you have on the go all kinds of storages from all kinds of providers,you win time and you reduce development cost,as nextcloud is open source and alot of people work on it and release new features,external providers you have all things in by implementing nextcloud
2)by nextcloud,your data is safe and encrypted,i don t think you would like google or dropbox looking at your personal files and pictures,if its not encrypted they can do that,via nextcloud that problem of privacy is solved too
when this is going to be done and be available,i will certainly buy it and i m sure others will too.