a few months ago, i created an encapsulated 624zz bearing idler for gt2 belt… when it gets to the right level, you simply put the bearing inside, and then continue to print to seal the bearing. check it out.
http://www.thingiverse.com/thing:492897
oooohh, thats pretty neat.
Have you ever tried a crowned pulley?
Self-centering and less friction !
This is one more advantage that 3D printing has over conventionally mass-produced parts.
@Erich_HaHaOh No, I haven’t tried that, but it does look pretty cool, when i designed this, i tried to make a idler with the least amount of footprint, and also, i designed in Sketch-up, but since then have moved to solid-works 
Maybe you can use (only) the idea of an unknown guy…
inside my idler is 2 steps, it locks the bearing inside. it has no way of misalignment, or removing the bearing (without force)
Keep on being inspired !