Investing in CW is useless as
1. If you know how to then any fertilizer factory can be used to produce what you want in days.
2. Days of Auschwitz like genocide are over. Now more insidious methods are prevalent. Like in England and Sweden.
3. When we use CW we end up hampering our efforts to move ahead and attack effectively while also becoming a rogue thus losing any support from any allies we may have.
Cost benefit analysis CW is a failed move of the desperately damned.
Well, that's not entirely true. In our context, while considering the mountain scenario, the Iraq-Iran war showed that CWs are pretty much useless in that situation. In the desert too, the high temperatures create problems for effective CW and the mechanized columns have both greater protection and mobility against CW.
However, the use of CW in the plains is a good possibility. Though the area is heavily populated on both sides of our western borders and militarily it will require favorable winds and very precise targeting, the army would be better prepared than the civilians through defensive measures like protective clothing.
The air force would have a problem because the high performance aircraft cannot be flown with protective gear and also the tolerance level of chemical exposure for fliers is very low. (They need very sensitive detectors to detect very low levels of nerve agents, levels which can cause myosis, blurred and dim vision because of pin-pointed pupils.)
The navy however, is well protected against CW.
Also, countries all around the world have used CWs in a conventional war, which should be an option in our arsenal too if a war does indeed break out. And virtually no consequences have followed after the use of CWs by nations as well:
• In 1968 during the Yemeni civil war. First use of CW after the world war.
• Extensive use of Agent Orange by US forces in Vietnam against the countrys ecology.
• In 1975 and 1981, in Laos, 261 attacks by Vietnamese and Laos forces caused 6,504 deaths using T2 toxin, nerve agents and riot control agents using sprays, rockets and bombs from AN-2 and captured American L-19 and T-28/41 aircraft.
• In 1979 and 1981, in Kampuchea, 124 attacks and 981 deaths through the T2 toxin, CW agents and riot control agents.
• In 1979 and 1981, in Afghanistan, 47 attacks by the Soviets caused 3,042 deaths using nerve agents, T2 toxin and riot control agents using aircraft and helicopters firing rockets, sprays and bombs.
• In 1982, a several thousand of their 7,000 to 10,000 casualties of Iranians were caused by the mustard gas. Iraq used Mi-8 helicopter sprayers and artillery shells.
• In 1984, in the Hawizeh marshes near Basra, mustard gas caused 12,000 to 20,000 casualties of Iranians.
• In 1988, mustard and nerve gas used on four occasions around Basra against a civilian population at Halabjah. Reports indicate use of phosgene and hydrogen cyanide by Iranians and blood agent by the Iraqi forces on 17 April at Al-Faw Peninsula. Iraq used mustard gas and nerve agents against Kurds in JuneJuly. From over a million military and civil casualties, 45,000 were caused by CW.
Ultimately, I would say it all boils down to choice: How much of a defensive capability and how much of CB ammunitions is required to protect the troops? What is the balance required to survive and sustain the forces on a modern battlefield?
The military generals must appreciate that CW agents can be defined, analysed and cleaned up. They are just chemical compounds like any other chemicals. Acids, fertilizers, pesticides you name it. It can be studied and handled safely.
The best approach here would be to have a big enough arsenal of credible offensive and defensive capability so that retaliation in kind is possible and it can thus force the enemy to return to conventional warfare after exchanging a few CW weapons if inevitable.