Family reunification/cohesion on a short term visa (C-category visa)?

I have obtained nulla osta from the prefettura for a family reunification. I would like to ask following two questions.

•    Does the Sportello Unico per l'immigrazione (Prefettura) need my documents legalization for the family reunification or the permesso di soggiorno of my family?
•    Can my wife obtain family reunification/family cohesion on a short-term visa (C-category visa or tourist visas) instead of long-term visa (D-category visa)?

Actually, the Consulate of Italy informed my wife that my documents (e.g. marriage certificate, family certificate, and birth certificates etc.) should be first legalized from the Consulate of Italy before applying to a long-term visa (D-category visa). However, this documents legalization/D-category visa process usually takes 1-3 months.  Hence, it seems to be that my wife cannot join me in Italy soon on this D-category visa?

Unfortunately, I cannot afford further delay in my family reunification as it could be very devastating for both my academic and personal life. Therefore, I am considering to invite my wife on a short-term visa (C-category visa). The short-term visa (C-category visa) do not need documents legalization and usually it takes only 15 days processing time. Once, my wife arrives in Italy then we will go to the Sportello Unico per l'immigrazione (Prefettura) in order to obtain family reunification/family cohesion since the prerequisites of family reunification/family cohesion are same which I already have fulfilled.

I hope someone will suggest me the best solution of my above-stated problem.