You just need a stronger first stage booster after all.
Russia's Bulava has a sharper head than both JL-2A and Trident II, but the sharper head will have less room for the MIRVed warheads.
currently only usa has deployed mirv missiles. russia has developed it but is currently upgrading missiles. china has proven it but still developing and will soon upgrade. i guess india should should prove it as soon as possible.