A weak economy is less able to fund a strong military. If the country signals a desire to use their military for conquest, it seems relatively sound to sanction the country as a means to constrain it first and foremost. I don't think the primary goal need be anything more than "make military conquest more expensive" and e.g., less likely to succeed. It's not hard to imagine what Russia would be doing right now if its economy were 10x as strong as it is.