Very cute little horse. I never deal with weanlings, but I got 2 unhandled yearlings. The main problem was at some point they start to test you (somehow mine started it at 3 years old), and that's when you really have to show the boundaries.
I don't think keeping separately form the herd is a good idea. My qh was kept separately for almost a year till I got her. She had NO understanding what so ever what means "hierarchy" in herd, which made it pretty dangerous when I let her out: she kept fighting and fighting to be alpha with very large (and mean) horses. And while she respects my space (and my mom's), she's testing EVERY other person coming into the field trying to bully them around.