I don't think the idea itself is bad, however, given the current anti-Pakistan government in Afghanistan, with its strong links to the Norther alliance warlords, there is no incentive for India to deploy troops (with Pakistan or separately) for COIN.
As I said earlier, India is denying Pakistan strategic space in Afghanistan without hemorrhaging blood or money. It has the space to support covertly destabilizing elements in Baluchistan - why ruin this favorable dynamic by deploying to fight the Taliban?
For Pakistan, fighting under a US umbrella (whether it is a joint force or not), which is what any engagement in Afghanistan will be perceived as, so long as the US is there, will only exacerbate the view amongst Pakistanis that the GoP is doing the US's bidding.
So I do not think Pakistan will deploy as long as the mission in Afghanistan remains under a US flag.