Hi Jack --
You may want to look at
iNIk.net, where Nik wrote a four-part series on adapting Entourage to fully implement GTD. I don't know entourage, so I can't evaluate what he's done, but I do know the work he did on kGTD extra functionality was first-rate. Maybe you can handle your situation within an augmented Entourage.
I don't think plain-vanilla GTD (or the current OmniF) has a good answer for tracking delegations with so many people. I adapted kGTD to solve a similar situation by adding metadata for Who the task is related to. I then could print out a list for each person of all the remaining tasks related to that person (and groups that they belonged to), sorted by context (or project).
This gave me, in effect, an agenda for each person while leaving the various tasks in different contexts. This is important to me because I have who are sometimes in 5 or 6 indepepndent roles in my life, so we have delegations and followups going both ways.
I hope that OmniF will let me add and sort by the information that is relevant to me.