Better to ask these type of questions in the BIM360 forum or contact your reseller.
But if I am correct all BIM360 subscriptions are user based.
As a first step you would need your BIM360 hub (get that when getting your subscriptions).
For BIM 360 Design you would need BIM 360 Docs & BIM 360 Design sub scription.
In a project you would assign the Revit modellers (by user name) a license for docs and design.
People who only need to view the models yoo could give them only docs license.
After project or when people quit the project you could recalim the license and hand it out to other user.
Basically all licenses are user based. But talk to your reseller to get the present and exact terms, this might change in time.
Louis

Please mention Revit version, especially when uploading Revit files.