So you have the top primarily a light blue color, very traditional supes, but along the obliquies and down into the legs you have darker shade of blue. Also a portion of the light blue dives below the belt as i felt it better integrated the top and bottom pieces together.
In keeping the belt the only justification i could think of is that the suit is actually two pieces, pants for the bottom and a shirt for the top rather than one piece like the FF4.
Overall i tried to keep it as close to the original as possible while changing up the lower half (primarily) to remove the shorts. the variations add pipings or various colors and dark arms. I'm not sure which would work best but i feel that a version of this costume could work well for a redesign.
Looking back on the design now, i would remove the belt or replace it with something else. I'd make a more dramatic color variation as well.