You are right that it has the ability to become self-sustaining and significant on its own power. It has great ports, some natural resources, a city with a long and interesting history that has regional historical, emotional and cultural attachments with Russians, Germans, Lithuanians and other Baltic people, Polish, etc, some nice coastal resorts and/or the potential to be such like Svetlogorsk (Rauschen), etc.
RentKaliningrad - Kaliningrad Guide
From what I understand, outside the city in the regional towns and rural areas of the oblast, plenty of German architecture remains despite the former Soviet policy to eradicate all elements of it, which I suspect occurred due to a myriad of reason such as saving costs, people already re-occupied them and/or they provided incentives for that due to their specific attractiveness or usefulness, they were pretty and liked locally, they could be refitted, they were 'out of the way' towns from most Western eyes, etc.
Many residents of the oblast also advocate for recharactertising and enjoying the Prussian history of the area too in rebuildings, local identity and cultural outreaches. Many even suggest changing the name of Kaliningrad back to Koenigsberg.