Whether it makes sense in everyone's eyes or not, you should be able to achieve some decent weight savings with your bottom bracket. A nutted spindle like yours will be solid all the way through, whereas a hollow spindle is lighter without giving up much (if any) strength. And the aluminum cups on higher-end bottom brackets save additional weight. On my rando bike, I went from a 286g Shimano UN55 to a 247g Tange-Seiki 7922, and that is in spite of going from a 107mm spindle to a 118mm spindle for a different crankset! So if you're not changing the length, you can do even better.