Aluminum Swinger (if I can find one)--- Lonestar and other companies make alum. swinger but they are for drag racing and would NEVER hold up to MX. Get a chromolly swinger. My chromolly swinger only weighs 9 pounds.
Hiper Carbon Fiber rims--- This is where you want to concentrate anything that spins around (rotating mass) you want to cut as much weight as possible but you can't sacrifice strength in MX.
Aluminum radiator--- PWR, Torch works, Ect but most are oversized to help reduce your heat not reduce weight but an engine 20 degrees cooler is worth a couple HP and 10 pounds is only worth 1 (3 pounds if rotating)
Custom aluminum subframe (would require frame mods, obviously)--- I don't think it would hold up but again look in to chromolly I would get a bolt on so if it bent it would be an easy replace.
Aluminum or Ti footpegs--- Alum pegs are easy to find but with MX I wouldn't want my anything but IMS peg JMO
Ti bolts on everything possible--- VERY EXPENSIVE JUST 1 CASTLE NUT FOR YOUR FRONT SPINDEL IS OVER $10
Remove lights (req'd for mx anyway)--- And go with a bare bones harness
Trim fenders? (how much weight does this save?)
Aluminum sprocket--- rotating weight
Aluminum shifter/brake pedal--- the only problem is during your lap the alum tend to bend but that might not be a problem for you
I would also consider and X-33 axle, wave rotors, lightest mx tires (no idea what), lonestar makes alum. lug nuts, and alum. or chromolly front hubs.
In order of importance as far as weight goes is rotating weight, unsprung weight, and sprung weight. Good luck with MX weight is not as important as strength. I would call GT Performance and talk to them.