Warning: math
Items remove:
Combined Storage Unit (-40 kg)
Desolation (-66 kg)
Rapid Destruction (-54 kg)
Total remove (-160 kg)
Items adding:
Energy Engine (+25 kg)
Night Fall (+49 kg)
Frantic Brute (+50 kg)
Reckless Beam (+35 kg)
Total adding (+159 kg)
Result: your mech got stronger and lighter by 1 kg!
( but you should upgrade your current mech first).