Raganui Minamoto
... Can you multi-class in 4e?
Hybridizing is blending two classes from the get-go, which can require some finesse. It is possible to further multiclass once you've hybiridized, but that's spreading yourself potentially rather thin. Hybrid rules are strict about not letting one class's abilities buff those of the other class.
In 3e terms, the alignment requirements of monk and barbarian are moot, monks can't level after multiclassing anyway. Monks lose no class abilities form becoming unlawful, simply the ability to gain more monk levels, which they've lost for becoming barbarian anyway. The trick is the order of level-gaining(and potential monastic training/Ascetic feats).