During writing an answer I received a note, that Jorsalfare was much quicker than me in answering

so here are mostly some rests of my old post:
Haladwin, your English is as good (or bad

) as mine. You must not reflect longer about your language, as here are a lot of posters at CFC (like both of us) that don´t have English as their mother language.
Resource systems to unlock units, frequently don´t work really well. Per example one of the most ambitious projects of a WW 2 scenario, SOE, nearly died by using such a system in the first versions, as we stumbled in the - at that time completely unknown - ghost resources bug in the programming of C3C. So normally much better is the system I have shown you in my last post of this thread for producing some limited special - mostly heavy - units in a WW 2 scenario. For normal units in a scenario this is not needed, as here the resource system is working well.
About preventing city razing in scenarios:
If you use preplaced buildings to produce these units and you set them to be wonders, the AI will not raze the city with that wonder (The AI will not raze any cities containing Great Wonders). If you will assure, that such a building can only been built by a special civ, give that civ an era none tech (let´s say Argentine flavour) and set a building, that it only can been built with that special tech for Argentine. Let´s call that building Argentine flag and give that building some culture, so it is razed, when another civ conquers a city with that flag in it. Now you can set any building, coming with any normal tech, to be only buildable by that civ by setting the Argentine flag as a building prerequisite for that other building.
One of the most efficient ways to prevent the razing of cities by the AI, as Jorsalfare posted above, is the so called No Raze Patch. This patch was done by Skyer2 and a downloadable version can be found here:
https://forums.civfanatics.com/resources/noraze-patch-for-conquests.14557/ . Antal1987 did a lot of very interesting patches, but not that one. All those patches of skyer2, Antal1987 and some No Raze - No city limits - no unit limit patches are based on a 'No CD Patch', done by Firaxis themselves, allowing you also to start a C3C game directly with that patched exe. The No Raze patch is essential for creating most WW2 mods and scenarios.