Tips on Collaboration using Office products, Browser version along with Desktop App

Does anyone have any tips on if a large group of people want to collaborate on a file and some of them want to use the browser version of an Office product, while others would prefer to use the desktop version?

Example: A team is working in a PowerPoint and 2 people are editing using PPT online and 2 other people are using the PPT desktop application. They are all making edits at the same time and if someone using the desktop app clicks Save before the others close and save the versions and version history can get messed up and it is difficult to determine who made what edits.

I have suggested that they either all need to be using the Browser version of an app so that they can utilize "Live" collaboration or if someone does need to use the desktop app they should lock the file while doing their edits. 

Looking for some more suggestions.

Thanks!