For a racing BMX, I see no reason why you couldn't use something fairly light like some bigger diameter Columbus Zona or maybe even Life/Foco if you're smooth.

I could be wrong though - I've never made a BMX, and most of the stock ones seem to be made from waterpipe in China and cost about 300 bucks.

I remember back in the day there was a cool one that had an Aluminium front end and a cromo bolt-on rear end. They were cool. So were the SE bikes.