Likely to be easiest for most users. Already being tried and tested at other universities. Least duplication of effort. Less planning required at unit level. Loss of control at unit level may limit current flexibility at a unit level.
Exchange needs careful consideration.
Potential major loss of service if central servers unavailable. Would require considerable planning and resources at central level. Multiple Forest Model Model 3 Multiple forest, single domain model. Each domain is in its own forest. This is essentially the same as Model 2, but at a unit level.