Adopting crypto would mean austerity for the Greeks beyond recognition. All fraud would immediately be forced out with the biggest economic reset conceivable. I wouldn't recommend this to the Greeks unless they cut down all government regulation except for the 10 commandments as well.
The government would not adopt crypto because just like you said that immediately gets rid of everyone's pensions and other entitlements.
HOWEVER, if they Grexit and entitlements get lost anyways, the people themselves may choose to adopt crypto aside from whatever new currency the Greek's start printing.