I made changes to 2 Creatures which can be downloaded and will work in your current game:
Fire Spider: Only 15% burn chance when Spitting Fire (still 30% in melee).
Ingeneer: Can only cast the Shock Grenade (blindness) once and cannot make more potions! The Shock Grenade range is 6 (was 7). His flame in 3 range is 15% stronger. Leadership as in vanilla (380 again). Price is 1250 (was 1850 in Trent and 1150 in vanilla). IMO it is more balanced now. The price and leadership is still arguable I guess. Feel free to comment. I guess the amount of Summoning could be reduced a bit?
Download:
Ingeneer and FireSpider.zip
The file ingeneer and spider_fire goes to Trent\Trent.kfs\Creatures, the last just goes to the Trent\Trent.kfs. Very important that you overwrite, if you don't see it overwrites, it won't work and probably crash.