Hmmm...I've been thinking...
I think I might convert my HQ Salamander, Opilio, back into being a griffon mortar. I can add it to my existing two in order to have a shiny new battery of three large, pinning, Str 5 ordnance barrage templates which re-roll the scatter dice.
I've always liked griffons:
Here's my Salamander as she currently is. I've never had a great deal of use for her - it was just an excuse for a conversion and a convenience for old Forge World armoured company lists: