Effective against whom, if i may ask? In my opinion, that'll only save your foes their nukes :/
The fact is, as most military guys know, that nukes are triggered in the air (and not on ground) for maximum effect. I doubt any country would use a 'nuke SAM' simply because it kills the purpose of the SAM. Even if the SAM doesn't do much material damage on the ground, at least it'll spread radioactive particles over own country. So neither India, nor Pakistan would go for that option.
A low yield nuke at med and high altitude is not a problem.You should refer to Soviet nuclear X-ray high altitude blast tests of 60's. The soviets found it to be extremely effective for potential ABM uses.
1.MIRVs
2. Stealthy terrain hugging cruise missles thats what we need!
babur is already there.