You know that if Israel takes out a missile site and accidentally releases chemicals from the Hamas warheads, Israel will be accused of using chemical weapons against Gaza, and no amount of proof will quiet the anti-Semetic leftists and Islamists.
While what you said is true, the major powers would be all over the chemical trace analysis of the agent, as it would invoke some very arcane and harsh sanctions against the manufacturer. Chemical weapons are recognized as WMD, and their use is a major “escalator”.
The US was very clear, for example, that if an enemy used chemical weapons on a US airfield, the US *would* reply with nuclear weapons.
The chemical weapons use during the Iran-Iraq war resulted in a lot of behind the scenes work, and the Russians in particular leaned on both sides to cut that crap out. And Russians are not subtle at all about some things.