On shield/blocking/stuff: the mod Timeless Kingdoms has blocking wakizashi, only it looks strange on your back when you holster it.
If it could be mixed with the standard wakizashi worn on the belt, it would be great.
However, dual wielding was not as common as pop culture suggests. There were no major school (Ryu) for it at the time of the mod (around 1560).
The wakizashi were used to fight in narrow places, commit seppuku, or was worn in places where no katana were allowed.
When a samurai drew both of his swords, you could make sure he was ready to die and will take as many with him as he can.
The wide renown of dual wielding samurai was born with Miyamoto Musashi. (I'm sure you all know him)