In blender I just use hardops to create bevels to achieve the effect you're talking about. Subdivision is usually not a good idea with hardsurface props.
Too preserve the silhouette, there's no getting around adding more cuts to achieve a 'smooth' finish without to much 'blockiness' evident for the player ingame via your proxy but also dependent on how close the camera is positioned as well?! so minor shading errors might not be that much of an isssue. Anyway your model is…