ICBM for tactical use is ridiculous.
If the mission is to flatten the North China Sea naval base, ICBM is the only option. Fighters dont have the reach, SSN's dont have the firepower - Which leaves us with ICBM's or SLBM's
Another thing is the fact that the payload is 1.5 tonnes and the MIRV configuration can be payload neutral with advanced versions of the missile having higher payloads just like more range.
But I agree that the 10 warhead configuration is the least likely to be used on the A5, but all the same we do need a 10 warhead configuration as that effectively means that the Arihant with 4 K4's can carry a total of upto 40 warheads, even if each is sub 100KT.