Check out my Power Up-Prototype Here are some of the parts modified:
1. Chest design
2. Back assembly
3. Arm assembly
4. Outer thigh side panel design and knee cap/armor
5. Inner thigh panels
6. Feet Design
7. Thrusters
8. Shoulders
9. New sets of guns (Big gun and twin rail gun)
10. Shoulder Spikes
More info of Custom Power Up