(assuming SS has really done for what he has done), SS should not be hanged. A life time prison is a bigger punishment for anybody, and that especially in Jails of Pakistan (or India).
Those who died in actions of this person already died, they would not become alive if he is hanged. He is served 22 years in Pakistan which is enough, i.e. his life has already been ruined and spent in jails. I think as a gesture, He should be released at a appropriate time, this will help in normalizing relations between the two countries. However, his release should only be made if he is no longer a threat to Pakistan or anybody.
Having said that, this hold to all criminals. Even I would say same for Ajmal Kasab. Prison him for life, this is a hard punishment than killing him at once. In south asia, we should give more respect to human lives, do not kill people, only prevent killings by imprisening the potentional killers or the killers.
It is time to abolish this medieval punishment. In countries with no capital punishment but a working justice system have a very lower crime and terrorism rate.
My $0.02