On a bmx headset could an integrated bearing set be replaced with a caged bearing set? I have a 20" eastern with a 1 1/8" integrated headset. The problem being is that my headset's top sealed bearing is no good and I only have some caged bearings currently on hand. Is there any possible way to replace the integrated with the caged bearings without having to change out any external parts i.e. forks?
Pictures would help here, but I am 95% sure that you won't be able to do that because there is no race for the caged bearings to ride on.  Sealed bearings have the race built in and the frame/headset will have a shoulder that the bearings butts up against, but not a race.
The other issue you will run into is that most sealed bearings are press-fit and the fork tube and headset will be sized accordingly.  You can't press-fit a caged bearing... 
Bottom line:  No.