How to bring two Entra ID tenants together for 365 apps and Entra ID Ent apps related collaboration?

Hi All,

I'm looking for an option to enable open collaboration between two Entra ID tenancies (two companies recently merged and now a single ORG). It seems Direct connect doesn't offer much to this context. 

I need to achieve the following at a minimum: 

1. Let users work as they're in one ORG. i.e. users from both ORGs can be browsed/discovered in 365 apps Outlook, Teams and Delve etc.. 

2. Granting user access across SharePoint, OneDrive etc.. has to be seamless. Users from both tenants will be appeared when trying to share, add permissions to items in SharePoint and OneDrive etc.. 

3. Outlook specially, should show users across both tenants (centralized GAL kind of a experience). I need to enable the full potential of calendar/mailbox sharing in Outlook across these two tenants so that users from both tenants get to share calendars, edit, see tasks, inbox via delegation etc... is this possible with B2B ? if not what are the potential alternatives ?

4. How will the trust work for Azure Enterprise Apps ? i.e. I have an app called "Interfox" but this has been only configured in the primary tenancy (Tenant A). How to leverage B2B options to leverage the “trust” between the tenancies so that InterFox would permit SSO [subject to the InterFox back end having knowledge of the Tenant-B.com emails]?

Thank you and really appreciate any thoughts !

Kev