I over complicated the problem, actually it’s totally possible with the CMS, I just got the answer from the Support.
This is possible currently with CMS content. You can add specific items to specific locales in your site. When you add an item to the primary locale, it is then created for all locales but you can then remove it from secondary locales if needed.
Also it works in the second locale, just add content there and don’t add it to the primary - works perfectly fine, all tested.