"Dual-wielding" has a lot of interesting potential and could be implemented in a couple different ways.
1) LMB controls left hand, RMB controls right. No blocking, only chambering. Potential to attack with each weapon in two different directions.
2) Both weapons attack on RMB and block with LMB. The main hand weapon can attack from the direction mouse is swung, the off-hand weapon swing direction can be linked to different mouse swing directions (Move mouse up - main hand overhead swings, off hand swings to right. Move mouse to right - main hand swings to left, off hand overhead swings, etc.). Basically, the off hand's attack direction is still determined by different mouse movements, but offset from the usual mapping.
3) Main hand does swings to left and overheads, off hand does swings to right and thrusts. Each weapon blocks respectively.
4) Additionally to the methods above, pressing "x" could change the stance to make the off hand into main hand and the main into off.