Mod idea: unique mods

Here's an idea. How about mods that are quite rare to get that only have a single effect and can't have secondary effects that are quite unique like:

• +10% counter chance
  
• +10% life steal
  
• +100% chance to get stealth for 1 turn when critically hit
  

Or simply copy an entire existing unique ability of some characters as a mod.
Downsides:

• no secondaries
  
• no set bonuses