(Disclaimer: I don't have much background in linguistics)
I think - if you are relating to agglutinantive and not polysynthetic languges - it would depend on what you are trying to build and the language too.
Staatspolizei (Secret State Police) may occur around words like-
The (whereas polizei would require and adjective before e.g. The Secret-State-Police vs The secret Police),
found (... Staatspolizei found and staats polizei found can have ambiguous interpretations if the language allows it, XYZ found something and XYZ found by me)
changing it's use totally.
whereas purushottama (man + ultimate/best/ideal = ideal man) is as you can see a compound of Noun + Adj. in that order, in Hindi , Sanskrit and other languages where it might be used purush uttama asti (please ignore grammatical/morphological endings if wrong) and purushottama asti have different meanings; The man is ideal and The ideal man (is) exists.
also purush uttama karya karta hai and purushottam karya karta hai mean The man does the best work and The ideal man does work respectively (The Adj. might be used to modify verb occuring in the same position)
The above distinctions thus, show that treating them as unigrams would be better than treating them as n-grams as far as the semantic role is concerned.
Hope that helps! :)