Hi Christian, I get you, absolutely right it needs to be a co-ordinated plan between all the people you work with. I work for a very large retailer, 85,000 staff, and we are getting there with moving all our files to OneDrive and SharePoint. If you have or can get Windows 10 then I would strongly suggest looking at the Files on Deman feature, it really fixes the issues you make around things behaving like a file share. Your boss would just see all his files in explorer, your 3D thingy would find the files it needs, in the background OneDrive Sync tool is pulling just the files needed and intelligently planning what to keep local and what to just be a marker. If you need a file that's not local, as you open it the operating system goes and fetches it seemlessly.
The ket points that drive our move, and may help your case are :-
1. Cost, it's simply far cheaper for us to buy SharePoint storage than reliable storage in our datacentre, about half the price.
2. Available from anywhere, like you pointed out already, this supports our companies strategy to allow people to work more flexibly in location, and contributes to a very large saving in reducing Office space.
3. Everything is versioned, everything is undeletable, far less work lost due to user mistakes
4. Easier to collaborate with partners in other companies, everything is a collaboration these days.
5. Powerful search to find files based on their names and content, thats also instant
6. Auditing and security compliance
etc.