Honestly, whenever I have pictured what I would do with Doom and Latveria, I always pictured maybe Latveria was a neighboring country to Sokovia, and Doom as a show of good faith maybe willingly opens his borders to Sokovian refugees and provides them housing or something in his country, while also maybe taking pieces of Ultron that were left beyond in Sokovia for study and maybe even elements of Ultron's abilities make their way into Doom's armor design. But of course, he improves upon them and makes it his own. But that would be as far as I would go with Stark's involvement in Doom's history.