@ Tom - That's one of the issues the hoster or automation vendor will need to solve in their end to end solution. There are a couple of ways to do it - LDS instances for each tenant, or removing LDAP browse altogether and relying on the enhanced EWS features in clients such as Outlook 2011 to resolve names via EWS, removing the need for LDAP altogether. The framework will lay out issues the hosters or ISV needs to consider such as this one, and leave them to design a supportable solution to each.
@ Andrew - UM is available in the Enterprise product - so if the solution contains UM, UM will be supported. ABP's work with UM, but any control panel vendor will have to ensure UM works as expected in their solution.
Just so we're all clear - we will be outlining the issues and challenges that need to be solved - and suggesting how to solve them - it is up to the vendors creating control panel solutions, or hosters writing their own solutions to figure out the exact way to solve it, and ensure it works in their environment.