Currently, we have many subsidiaries each with stand-alone Active Directory Domain. The plan is to migrate all to Office365 and implement Skype for Business (S4B) but maintain the ability for each subsidiary to manage their own AD and S4B. What is more practical:
1) Have one top level O365 Domain with subsidiary subdomains and one instance of S4B serving all domains?
2) Have one top level O365 Domain with subsidiary subdomains, where each subsidiary domain has a separate instance of S4B?
3) Have a separate O365 Domain for each subsidiary each with an instance of S4B then federate with all domains?