this suggestion is to create a new spell, call it something like Fuse Blades.
How it works: It works on Spirit Blades or Elemental Blades, and allows the wizard who has a set of these blades equipped to choose two of them, and combine them into a new blade of the third type.
So for example a Storm Wiz with an elemental blade would choose to combine the ice and fire blades, and the resulting blade would be a new storm blade that would stack with the remaining storm blade.
Maybe it would be a shadow spell and cost one shadow pip.
Well thought out spell and would be extremely useful, however I don't think it would be practical to choose the new blade type. Something like the storm wizard selecting the fire and ice blade which fuses them into a 30% balance blade perhaps. Just seems like it would take to much time to have to select what school the blade turns in to since you only have 30 seconds.