Looking for my next big build!

I'm having an absolute blast painting my Warp Lightning Cannon build, and looking for my next project! I love working within the Skaven aesthetic so I'd really like to start on another crazy warmachine.

I'd like to do something a little more out-there, this time, and was wondering if anybody knows of any interesting fleeting references in the lore to machines or weapons that don't have miniatures or rules representation.

Ideally I'd like to build something of around Screaming Bell size, and more machine than organic. Combining existing ideas might be a good avenue - a gnawhole projector that teleports swarms of rats directly into the enemy, or maybe a machine that throws giant warpstone shuriken - anything goes!

Not particularly fussed about possible rules or game usability.

In advance: the cannon is scratchbuilt, not printed. There is no STL.

Would love to hear any thoughts or suggestions.

Cheers!