This is a really great thread o' discussion.
Just to follow-up on all of the latest contributions:
And you'll probably want to volunteer a lead "visionary" in the team to act as TiddlyWiki custodian/librarian/evangelist.
I tend to see your project very much like a software development project, but mostly all about gathering requirements and prototyping, all about assessing needs. (I get right giddy about those activities. So much fun !!!)
What I have seen in software development, you often have higher up folk who want certain information, and applications get created for staff to enter data with the goal of providing management with the information management needs.
Staff often wind up in the unenviable position of experiencing use of the system as "extra work", and the system to be used because "somebody said so." Yuck.
To me, and right out of the gate, any thing created for people to use needs to provide immediate benefit to those people. It has to be something that isn't "extra work", but rather something that provides value to each one of them. When you take care of the little dimes, the dollars take care of themselves, in a way.
So whatever the "big goal/purpose", it can be much easier to get there when other "little goals/purposes" are supported first as something that leads to success with the meatier goal.
Now, I have not yet had my first cup of morning coffee. Please take all of that philosophical mumbo-jumbo of mine with a bucket of salt.