Considering aggregation levels
The FTE calculation, as we have designed it, computes the FTEs needed at the level of project type. This means that we simply add the FTE numbers for all projects with the same type. It is a business consideration as to whether this is what the organization really wants.
For example, if an A1 project in Paris and an A1 project in London will run at the same time and each needs a 0.5 FTE project manager, we need 1 full-time project manager in total. While this is mathematically correct, you may argue that a single project manager will not be able to manage both projects. We may need boots on the ground, which practically excludes having someone travel between Paris and London all the time. The result would be that we need, in fact, two project managers.
The simple solution to this would be to do the calculation on a by-location basis, adding another iteration to the measure. However, even if we compute 0.5 FTE twice, the end result is still 1...