Have you considered the AeroFS (https://www.aerofs.com/pricing https://www.aerofs.com/pricing)? I have not used AeroFS, but it would be on my list to evaluate f

Have you considered the AeroFS (https://www.aerofs.com/pricing https://www.aerofs.com/pricing)? I have not used AeroFS, but it would be on my list to evaluate for your use case, especially if external storage is undesirable. Pricing seems in line with Dropbox for Business, although this does not take into account the cost of maintaining your own storage.