Suppose it depends the level of granularity required on reporting (and
the reasons for this need). If you need task names, then yes, OLAP is
restrictive. However, if it is task categorisations (eg which phase a
task is in, etc), then you could extend OLAP to do this.
I worry about detailed granular data for senior level reporting as the
data can often be in flux, leading to mixed messages.
However if you need to see generic task level data you can use the
Resource availability view from Resource Centre (the table section) to
see these assignments. Alternatively you could use a "real" resource
to capture the data for view in Resource Assignments as you suggest
though you would probably want to categorise them using an outline code
to seperrate them from your individuals in PWA/Portfolio Analyser
views.