I can't believe how hard the following problem is turning out to be.
We are a small company with people hither and yon (for various reasons) who need to see/work-on the same "documents". In a normal Windows Explorer kinda way (not some over-there-in-the-browser kinda way) and with (near-)LOCAL DISK speed. (I do not want to hear the word 'WebDAV' ever again.)
Yes, they always need to see the "latest" version at all times. (No, they do not want to click an 'Update' button.)
They need to be told "Whoa! Two of you are trying to write that thing at once!"
Different (changing) groups of people need to see different groups of documents. Only finance people can see finance documents, etc.
An "admin" needs to be able to login, get some oversight of things, and change stuff, e.g. shut off the person who just left the company.
Windows, Macs and Linux, please. (OK, OK... we're flexible.)
I would have thought the above would be the FIRST THING any "cloud storage" wannabee might turn his hand to.
Obvious "solutions": NONE (that I've found). More as I find it.