You should patch dromed 2 and Thief 2 (not sure is that needed, but...)

The BCB gamesystem includes
-Burrick (thanks to Belboz)
-Crayman and Bugbeast (thanks to Spitter and HunterByNite) 'with bugshots'
-Hammer mage 
-Craybeast (all the sounds work now)
-Spiderbeast
-FireElemental
-Holy Font

Install

Unzip the file to your Thief 2 folder. 

-Open dromed and load your level and write set_gamesys BCB (In input window)
-Save mission
-Open dromed
-load your level

If you can't hear any sounds from the monsters recompute pathfinding.