After struggling with a Kea and Minecart problem that repeatedly crashed my game (until I decided to bury the damned (in many ways) minecart once and for all in a puddle, avoiding the bug initially, and then sealing it inside an obsidian black-box (DFHack, Liquids-made monolith), to prevent the bug once and for all); I thought up a good couple more plugins.
A Thief's Eye kind of plugin. Simply put, it lists your most valuable, or most-likely-to-be-taken items (or children or animals), be it by kobold or kea, or any other kind of theif. And if possible, also markup the odds of a child thief and/or the intended target child, along with the items. If possible as well, find a way to clear the "attraction" to said item of the creature in question hunting it down. kill their interest in the item in question so they can stop pursuing it, even if it means they'll still be hanging around idly as if they were scared off from the steal.
I don't think it's possible, especially since I also don't know enough programming to know how it would work or be developed, but an error-checker of sorts to scan all items and characters for any gamebreaking flaws/bugs (like my minecart that kills my game anytime it goes missing/destroyed/deleted (via DFHack)). It's mostly informative, But it can also auto-dump (or auto-assign dump/forbid) any problem-items so they can't be tampered with further. Autodump can also be given a problem-item autodump function as well, though it would have to work in tandem with the scanner to work properly.
And one more comes to mind, but a siege/ambush heads-up plugin would be interesting, as if your dwarves (especially in aboveground forts) can see the armies coming in from over the horizon. Basically, it would tell you at least the chances of it happening, based on your fort value, or whatever values either ambush or siege responds to. Of course, it doesn't need to be a HUD or sorts, but a DFHack command. Especially also helpful if you want to know what faction is coming after you if there's more than one civ pissed off at your mere existence. Prepare accordingly.
EDIT:
I just thought up another one: Death-Note
Highlight the character you want to kill, and it'll markup the heart or most-valuable organ of the creature as non-existant, or destroyed/broken, thereby killing the creature immediately. Named after Death-Note, since it's mostly by heart-attack the creatures in question are killed by. Death may not be immediate for some, and I am uncertain about the undead, and how it may affect necromancy. Nonetheless, I think this would be a fun, yet exploitable, plugin. Gore can be an option, which explodes the creature on the spot, as if they ate a full serving C4-potato salad.