It there 'any' variation in the look of the surface of the object that can be enhanced? ie. if you really cranked up the apparent contrast from your RAW images (from curve adjustments, pulling down shadows/blacks, etc), can you get any extra perceptible detail out of the images that can give Agisoft a bit more to grab details from? You can always swap out normally developed images before you generate the texture, but an overcranked detail version of the images can help quite a bit to generate better geometry.