I feel like the combo system in place actually lends itself really well to this idea.

Thinking along the lines of...

>Thaumaturge targets Gladiator with Thunder Spell.

>Lightning effect goes off around the Gladiator's sword - he now has a combo timer activated (similar to when doing a self combo).

>Gladiator then has that 10 second time period to perform a weapon skill (Specific? Any?) that will have the added damage and effect of thunder.

Simple and uses a system that already in place.