Im challenging to make a Posadist the leader of a country.
At this point nothing is to crazy, just make it plausible as our timeline.
I'd choose an mountainous country/region of Latin America like Bolivia, or an alt-Sendero Luminoso or FARC that's more successful. They could use drug trafficking to pay for weaponry and turn remote terrain into an advantage (a communist analog of the Taliban in Afghanistan).
Considering the Posadist concept that nuclear war is inevitable or even desirable to end capitalism, they should probably choose a country with a relatively rural, dispersed population that can survive a nuclear conflict. An extremely urbanized, country like Japan or Argentina that depends on one urban mega region is a poor choice. An extremely rural country with a dispersed population in Central Africa or the Sahel could be another good base of operations. A posadist regime would probably aim for a Pol Pot style
Year Zero that empties the cities.
If they want to provoke a nuclear war between the two major sides, they'd need to make some strange bedfellows. North Korea, Tito, Ceausescu, Qaddafi's Libya would all be sympathetic to a regime trying to get nuclear weapons. I expect a Posadist regime to back leftist, neofascist, and Islamist terrorist groups to raise as much havoc as possible and bring the superpowers into conflict. The Red Army Gang or Al Qaeda would be useful proxies to create a Sarajevo moment between the nuclear powers. The closest ATL example of a James Bond villain like that is the movie
The Sum of All Fears where an Austrian neo-Nazi tries to trigger a nuclear war between the US and Russia.