I thought Vargas in Turkish NT was a done deal. As much as i know, she spends her off-seasons in Belgrade, but so do some other Cuban players like Casanova e.g. . I think it is something that SBCommunity agency organizes.
As Bogdan said, laws are applied exclusively here . There are cases of someone getting a passport out of the blue, but for ordinary people the requirements are as in the most countries. This picture sums it up
I was getting excited that Serbia might in future abolish 'two liberos' system, but apparently it ain't happening. The only way i see Terzic not using two power players are if he doesn't find decent replaments for libero and setter positions. Vargas with just her serve would be addition to any NT but how Terzic wants to use her, is very risky